Resist composition, method of forming resist pattern, compound and acid generator

ABSTRACT

A resist composition including: a base component (A) which exhibits changed solubility in an alkali developing solution under action of acid; and an acid-generator component (B) which generates acid upon exposure, wherein said acid-generator component (B) comprises an acid generator (B1) including a compound represented by general formula (b1-11) shown below:
         wherein R 7″  to R 9″  each independently represent an aryl group or an alkyl group, wherein two of R 7″  to R 9″  may be bonded to each other to form a ring with the sulfur atom, and at least one of R 7″  to R 9″  represents a substituted aryl group having a group represented by general formula (I) shown below as a substituent; X −  represents an anion; and R f  represents a fluorinated alkyl group.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist composition, a method offorming a resist pattern using the resist composition, a compound usefulas an acid generator for a resist composition, and an acid generator.

Priority is claimed on Japanese Patent Application No. 2008-184185,filed Jul. 15, 2008, Japanese Patent Application No. 2008-271120, filedOct. 21, 2008, and Japanese Patent Application No. 2009-123095, filedMay 21, 2009, the contents of which are incorporated herein byreference.

2. Description of Related Art

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure to radial rays such as light or electronbeams through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

For miniaturization of semiconductor devices, shortening of thewavelength of the exposure light source, and increasing of the numericalaperture (NA) of the projector lens have progressed. Currently, exposureapparatuses in which an ArF excimer laser having a wavelength of 193 nmis used as an exposure light source and having a NA=0.84 have beendeveloped. As shortening the wavelength of the exposure light sourceprogresses, it is required to improve various lithography properties ofthe resist material, such as the sensitivity to the exposure lightsource and a resolution capable of reproducing patterns of minutedimensions. As a resist material which satisfies these conditions, achemically amplified resist is used, which includes a base resin thatexhibits a changed solubility in an alkali developing solution underaction of acid and an acid generator that generates acid upon exposure(Patent Document 1).

Currently, resins that contain structural units derived from(meth)acrylate esters within the main chain (acrylic resins) are nowtypically used as base resins for resists that use ArF excimer laserlithography, as they exhibit excellent transparency in the vicinity of193 nm.

Here, the term “(meth)acrylic acid” is a generic term that includeseither or both of acrylic acid having a hydrogen atom bonded to theα-position and methacrylic acid having a methyl group bonded to theα-position. The term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position. The term “(meth)acrylate” is a genericterm that includes either or both of the acrylate having a hydrogen atombonded to the α-position and a methacrylate having a methyl group bondedto the α-position.

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2003-167347

SUMMARY OF THE INVENTION

As the above-mentioned miniaturization of resist patterns has continuedto progress, in the formation of a resist pattern, problems have arisen,including formation of T-top shapes in line and space patterns andoccurrence of “Not Open” defects in contact hole patterns, in which aportion of, or all of, a hole pattern is not open. In particular, theoccurrence of “Not Open” defects in contact hole patterns has become asignificant issue. Therefore, development of a novel material which iscapable of solving such problems has been demanded.

The present invention takes the above circumstances into consideration,with an object of providing a novel compound useful as an acid generatorfor a resist composition, an acid generator including the compound, aresist composition containing the acid generator, and a method offorming a resist pattern that uses the resist composition.

For solving the above-mentioned problems, the present invention employsthe following aspects.

Specifically, a first aspect of the present invention is a resistcomposition including a base component (A) which exhibits changedsolubility in an alkali developing solution under action of acid and anacid-generator component (B) which generates acid upon exposure,

the acid-generator component (B) including an acid generator (B1)including a compound represented by general formula (b1-11) shown below.

wherein R^(7″) to R^(9″) each independently represents an aryl group oran alkyl group, wherein two of R^(7″) to R^(9″) may be bonded to eachother to form a ring with the sulfur atom, and at least one of R^(7″) toR^(9″) represents a substituted aryl group having a group represented bygeneral formula (I) shown below as a substituent; and X⁻ represents ananion.

[Chemical Formula 2]—O—R^(f)   (I)wherein R^(f) represents a fluorinated alkyl group.

A second aspect of the present invention is a method of forming a resistpattern, including: applying a resist composition of the first aspect toa substrate to form a resist film on the substrate; subjecting saidresist film to exposure; and subjecting said resist film to alkalideveloping to form a resist pattern.

A third aspect of the present invention is a compound represented bygeneral formula (b1-11) shown below.

wherein R^(7″) to R^(9″) each independently represent an aryl group oran alkyl group, wherein two of R^(7″) to R^(9″) may be bonded to eachother to form a ring with the sulfur atom, and at least one of R^(7″) toR^(9″) represents a substituted aryl group having a group represented bygeneral formula (I) shown below as a substituent; and X⁻ represents ananion.

[Chemical Formula 4]—O—R^(f)   (I)wherein R^(f) represents a fluorinated alkyl group.

A fourth aspect of the present invention is an acid generator includingthe compound of the third aspect.

In the present description and claims, unless specified otherwise, theterm “alkyl group” is deemed to include linear, branched and cyclic,monovalent saturated hydrocarbon groups.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified.

A “lower alkyl group” is an alkyl group of 1 to 5 carbon atoms.

A “halogenated lower alkyl group” is an alkyl group in which some or allof the hydrogen atoms have been substituted with halogen atoms, whereinexamples of the halogen atoms include a fluorine atom, chlorine atom,bromine atom and iodine atom.

The term “aliphatic” is a relative concept used in relation to the term“aromatic”, and defines a group or compound that has no aromaticity.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a resin component (a polymer or copolymer).

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

According to the present invention, there are provided a novel compounduseful as an acid generator for a resist composition, an acid generatorincluding the compound, a resist composition containing the acidgenerator, and a method of forming a resist pattern using the resistcomposition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram describing an advancing angle (θ1), a receding angle(θ2) and a sliding angle (θ3).

DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS

1: Liquid droplet; 1 a: Bottom edge; 1 b: Top edge; 2: Flat surface; θ1:Advancing angle; θ2: Receding angle; θ3: Sliding angle

DETAILED DESCRIPTION OF THE INVENTION

<<Resist Composition>>

A resist composition of the present invention includes a base component(A) (hereafter, frequently referred to as “component (A)”) whichexhibits changed solubility in an alkali developing solution under theaction of acid and an acid generator component (B) (hereafter,frequently referred to as “component (B)”) which generates acid uponexposure.

In the resist composition, when acid is generated from the component (B)upon exposure, the action of the generated acid causes a change in thesolubility of the component (A) in an alkali developing solution. As aresult, during resist pattern formation, when a resist film formed usingthe resist composition of the present invention is subjected toselective exposure, the solubility in the alkali developing solution ofthe exposed portions increases, whereas the solubility in the alkalideveloping solution of the unexposed portions remains unchanged, meaningalkali developing of the resist film can then be used to form a resistpattern.

<Component (A)>

As the component (A), an organic compound typically used as a basecomponent for a chemically amplified resist composition can be usedalone, or two or more of such organic compounds can be mixed together.

Here, the term “base component” refers to an organic compound capable offorming a film, and is preferably an organic compound having a molecularweight of 500 or more. When the organic compound has a molecular weightof 500 or more, the film-forming ability is improved, and a resistpattern of nano level can be easily formed.

The organic compounds having a molecular weight of 500 or more that maybe used as the base component are broadly classified into low molecularweight organic compounds having a molecular weight of 500 to less than2,000 (namely, “low molecular weight materials”) and high molecularweight organic compounds having a molecular weight of 2,000 or more(namely, “polymeric materials”). Generally, a non-polymer is used as thelow molecular weight material. A resin (a polymer or copolymer) is usedas the polymeric material. With respect to the aforementioned resin, the“molecular weight” refers to the polystyrene equivalent weight averagemolecular weight determined by gel permeation chromatography (GPC).Hereafter, the simplified term “resin” refers to a resin having amolecular weight of 2,000 or more.

As the component (A), a resin which exhibits changed alkali solubilityunder the action of acid or a low molecular weight material whichexhibits changed alkali solubility under the action of acid may be used.Alternatively, a combination of these materials may also be used.

When the resist composition of the present invention is a negativeresist composition, for example, as the component (A), a base componentthat is soluble in an alkali developing solution is used, and across-linking agent is blended in the negative resist composition.

In the negative resist composition, when acid is generated from thecomponent (B) upon exposure, the action of the generated acid causescross-linking between the base component and the cross-linking agent,and the cross-linked portion becomes insoluble in an alkali developingsolution. Therefore, in the formation of a resist pattern, by conductingselective exposure of a resist film formed by applying the negativeresist composition onto a substrate, the exposed portions becomeinsoluble in an alkali developing solution, whereas the unexposedportions remain soluble in an alkali developing solution, and hence, aresist pattern can be formed by alkali developing.

Generally, as the base component for a negative resist composition, aresin that is soluble in an alkali developing solution (hereafter,referred to as “alkali-soluble resin”) is used.

As the alkali-soluble resin, it is preferable to use a resin having astructural unit derived from at least one of α-(hydroxyalkyl)acrylicacid and a lower alkyl ester of α-(hydroxyalkyl)acrylic acid, as itenables formation of a satisfactory resist pattern with minimalswelling. Here, the term “α-(hydroxyalkyl)acrylic acid” refers to one orboth of acrylic acid in which a hydrogen atom is bonded to the carbonatom on the α-position having the carboxyl group bonded thereto, andα-hydroxyalkylacrylic acid in which a hydroxyalkyl group (preferably ahydroxyalkyl group of 1 to 5 carbon atoms) is bonded to the carbon atomon the α-position.

As the cross-linking agent, typically, an amino-based cross-linkingagent such as a glycoluril having a methylol group or alkoxymethyl groupis preferable, as it enables formation of a resist pattern with minimalswelling. The amount of the cross-linking agent added is preferablywithin the range from 1 to 50 parts by weight, relative to 100 parts byweight of the alkali-soluble resin.

When the resist composition of the present invention is a positiveresist composition, as the component (A), a base component that exhibitsincreased solubility in an alkali developing solution under the actionof acid is used. More specifically, the base component is substantiallyinsoluble in an alkali developing solution prior to exposure, but whenacid is generated from the component (B) upon exposure, the action ofthis acid causes an increase in the solubility of the base component inan alkali developing solution. Accordingly, during resist patternformation, when a resist film formed by applying the positive resistcomposition to a substrate is selectively exposed, the exposed portionschange from being substantially insoluble in an alkali developingsolution to being alkali-soluble, whereas the unexposed portions remainalkali-insoluble, meaning a resist pattern can be formed by alkalideveloping.

The resist composition of the present invention is preferably a positiveresist composition. That is, in the resist composition of the presentinvention, the component (A) is preferably a base component whichexhibits increased solubility in an alkali developing solution underaction of acid.

The component (A) may be a resin component (A1) which exhibits increasedsolubility in an alkali developing solution under action of acid(hereafter, referred to as “component (A1)”), a low molecular weightcompound which exhibits increased solubility in an alkali developingsolution under action of acid (hereafter, referred to as “component(A2)”), or a mixture of the component (A1) and the component (A2).

[Component (A1)]

As the component (A1), a resin component (base resin) typically used asa base component for a chemically amplified resist composition can beused alone, or two or more of such resin components can be mixedtogether.

In the present invention, it is preferable that the component (A1)include a structural unit derived from an acrylate ester.

In the present descriptions and the claims, the term “structural unitderived from an acrylate ester” refers to a structural unit which isformed by the cleavage of the ethylenic double bond of an acrylateester.

The term “acrylate ester” is a generic term that includes acrylateesters having a hydrogen atom bonded to the carbon atom on theα-position, and acrylate esters having a substituent (an atom other thana hydrogen atom or a group) bonded to the carbon atom on the α-position.As the substituent, a lower alkyl group or a halogenated lower alkylgroup can be mentioned. With respect to the “structural unit derivedfrom an acrylate ester”, the “α-position (the carbon atom on theα-position)” refers to the carbon atom having the carbonyl group bondedthereto, unless specified otherwise.

With respect to the acrylate ester, specific examples of the lower alkylgroup for the substituent at the α-position include linear or branchedalkyl groups such as a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, and a neopentyl group.

Specific examples of the halogenated lower alkyl group include groups inwhich some or all of the hydrogen atoms of the aforementioned “loweralkyl group for the substituent at the α-position” are substituted withhalogen atoms. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

In the present invention, it is preferable that a hydrogen atom, a loweralkyl group or a halogenated lower alkyl group is bonded to theα-position of the acrylate ester, more preferably a hydrogen atom, alower alkyl group or a fluorinated lower alkyl group. In terms ofindustrial availability, a hydrogen atom or a methyl group isparticularly desirable.

It is particularly desirable that the component (A1) have a structuralunit (a1) derived from an acrylate ester containing an acid dissociable,dissolution inhibiting group.

Further, in addition to this structural unit (a1), this polymerpreferably also has a structural unit (a2) derived from an acrylateester that contains a lactone-containing cyclic group.

Moreover, in addition to the structural unit (a1), or in addition to thecombination of the structural units (a1) and (a2), the above-mentionedcomponent (A1) (polymer) preferably also has a structural unit (a3)derived from an acrylate ester that contains a polar group-containingaliphatic hydrocarbon group.

Furthermore, the above-mentioned component (A1) (polymer) may alsoinclude a structural unit (a4) that is different from the aforementionedstructural units (a1) to (a3).

Structural Unit (a1):

The structural unit (a1) is a structural unit derived from an acrylateester that contains an acid dissociable, dissolution inhibiting group.

The acid dissociable, dissolution inhibiting group within the structuralunit (a1) has an alkali dissolution inhibiting effect that renders theentire component (A1) insoluble in an alkali developing solution priorto dissociation, and then following dissociation under action of acid,increases the solubility of the entire component (A1) in the alkalideveloping solution. There are no particular limitations on the aciddissociable, dissolution inhibiting group within the structural unit(a1), and any of the groups that have been proposed as acid dissociable,dissolution inhibiting groups for the base resins of chemicallyamplified resists can be used. Generally, groups that form either acyclic or chain-like tertiary alkyl ester with the carboxyl group of the(meth)acrylic acid, and acetal-type acid dissociable, dissolutioninhibiting groups such as alkoxyalkyl groups are widely known. Here, theterm “(meth)acrylic acid” is a generic term that includes either or bothof acrylic acid having a hydrogen atom bonded to the α-position andmethacrylic acid having a methyl group bonded to the α-position.

A tertiary alkyl ester describes a structure in which an ester is formedby substituting the hydrogen atom of a carboxyl group with a chain-likeor cyclic tertiary alkyl group, and a tertiary carbon atom within thechain-like or cyclic tertiary alkyl group is bonded to the oxygen atomat the terminal of the carbonyloxy group (—C(O)—O—). In this tertiaryalkyl ester, the action of acid causes cleavage of the bond between theoxygen atom and the tertiary carbon atom. The chain-like or cyclic alkylgroup may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable, dissolutioninhibiting group” is not limited to be constituted of only carbon atomsand hydrogen atoms (not limited to hydrocarbon groups), but ispreferably a hydrocarbon group. Further, the “hydrocarbon group” may beeither saturated or unsaturated, but is preferably saturated.

Examples of the aliphatic branched acid dissociable, dissolutioninhibiting group include groups represented by a formula—C(R⁷¹)(R⁷²)(R⁷³). In this formula, R⁷¹ to R⁷³ each independentlyrepresents a linear alkyl group of 1 to 5 carbon atoms. The grouprepresented by —C(R⁷¹)(R⁷²)(R⁷³) preferably contains from 4 to 8 carbonatoms, and specific examples include a tert-butyl group,2-methyl-2-butyl group, 2-methyl-2-pentyl group, and 3-methyl-3-pentylgroup, and a tert-butyl group is particularly desirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

In the aliphatic cyclic group-containing acid dissociable, dissolutioninhibiting group, the aliphatic cyclic group may or may not have asubstituent. Examples of substituents include lower alkyl groups of 1 to5 carbon atoms, a fluorine atom, fluorinated lower alkyl groups of 1 to5 carbon atoms, and an oxygen atom (═O).

The aliphatic cyclic group may be a hydrocarbon group formed solely fromcarbon and hydrogen (alicyclic group), or a heterocyclic group in whicha portion of the carbon atoms that constitute the ring structure of analicyclic group have been substituted with a hetero atom such as anoxygen atom, a nitrogen atom, or a sulfur atom. The aliphatic cyclicgroup is preferably an alicyclic group.

The aliphatic cyclic group may be either saturated or unsaturated,although a saturated group is preferred, as such groups exhibit superiortransparency to ArF excimer lasers and the like, and also exhibitexcellent resolution and depth of focus (DOF) and the like.

The number of carbon atoms within the aliphatic cyclic group ispreferably within a range from 5 to 15.

Examples of the aliphatic monocyclic groups include groups in which oneor more hydrogen atoms have been removed from a cycloalkane. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from cyclopentane or cyclohexane, and a group in which twohydrogen atoms have been removed from cyclohexane is preferable.

Examples of the aliphatic polycyclic groups include groups in which oneor more hydrogen atoms have been removed from a bicycloalkane,tricycloalkane, tetracycloalkane or the like. Specific examples includegroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

Of these, groups in which two hydrogen atoms have been removed fromadamantane, norbornane or tetracyclododecane are readily availableindustrially, and are consequently preferred. Of these monocyclic andpolycyclic groups, a group in which two hydrogen atoms have been removedfrom adamantane or norbornane is particularly desirable.

Examples of aliphatic cyclic group-containing acid dissociable,dissolution inhibiting groups include (i) groups having a tertiarycarbon atom within the ring structure of an aliphatic cyclic group; and(ii) groups having an aliphatic cyclic group, and a branched alkylenegroup containing a tertiary carbon atom bonded to the aliphatic cyclicgroup.

Specific examples of the groups (i) include groups represented bygeneral formulas (1-1) to (1-9) shown below.

Specific examples of the groups (ii) include groups represented bygeneral formulas (2-1) to (2-6) shown below.

wherein R¹⁴ represents an alkyl group, and g represents an integer of 0to 8.

wherein R¹⁵ and R¹⁶ each independently represents an alkyl group.

As the alkyl groups of R14 to R16, lower alkyl groups are preferred, andlinear or branched alkyl groups are particularly desirable. Specificexamples include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group. Ofthese, a methyl group, an ethyl group or an n-butyl group is preferred,and a methyl group or an ethyl group is particularly desirable.

In general formula (1-2), g is preferably an integer of 0 to 5, morepreferably an integer of 1 to 3, and most preferably 1 or 2.

Specific examples of the acid dissociable, dissolution inhibiting grouprepresented by formula (1-2) include a 1-methyl-1-cyclobutyl group, a1-ethyl-1-cyclobutyl group, a 1-isopropyl-1-cyclobutyl group, a1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-isopropyl-1-cyclopentyl group, a 1-methyl-1-cyclohexyl group, a1-ethyl-1-cyclohexyl group, a 1-isopropyl-1-cyclohexyl group, a1-methyl-1-cycloheptyl group, a 1-ethyl-1-cycloheptyl group, a1-isopropyl-1-cycloheptyl group, a 1-methyl-1-cyclooctyl group and a1-ethyl-1-cyclooctyl group.

An “acetal-type acid dissociable, dissolution inhibiting group”generally substitutes a hydrogen atom at the terminal of analkali-soluble group such as a carboxyl group or hydroxyl group, so asto be bonded with an oxygen atom. When acid is generated upon exposure,the generated acid acts to break the bond between the acetal-type aciddissociable, dissolution inhibiting group and the oxygen atom to whichthe acetal-type, acid dissociable, dissolution inhibiting group isbonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by general formula (p1) shown below.

wherein Y represents a linear or branched alkyl group or an aliphaticcyclic group; n represents an integer of 0 to 3; R^(1′) and R^(2′) eachindependently represents a linear or branched alkyl group or a hydrogenatom; and Y and R^(1′) may be bonded to each other to form an aliphaticcyclic group.

In general formula (p1) above, Y represents a linear or branched alkylgroup, or an aliphatic cyclic group.

When Y represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 15 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, still more preferably an ethyl group or a methylgroup, and most preferably an ethyl group.

When Y represents an aliphatic cyclic group, as the aliphatic cyclicgroup, any of the aliphatic monocyclic/polycyclic groups which have beenproposed for conventional ArF resists and the like can be appropriatelyselected for use. For example, the same groups described above inconnection with the “aliphatic cyclic group” can be exemplified.

The aliphatic cyclic group for Y preferably has 4 to 15 carbon atoms,more preferably has 4 to 12 carbon atoms, and most preferably has 5 to10 carbon atoms. Examples thereof include groups in which one or morehydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group. Specific examples include groups inwhich one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane or cyclohexane, and groups in whichone or more hydrogen atoms have been removed from a polycycloalkane suchas adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these, a group in which one or more hydrogenatoms have been removed from adamantane is preferable.

In general formula (p1), n is an integer of 0 to 3, preferably aninteger of 0 to 2, more preferably 0 or 1, and most preferably 0.

R^(1′) and R^(2′) each independently represents a linear or branchedalkyl group or a hydrogen atom.

As the linear or branched alkyl group for R^(1′) and R^(2′), a loweralkyl group is preferable. As the lower alkyl group, the same as thelower alkyl groups for R described later can be exemplified, and amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

In the present invention, it is preferable that at least one of R^(1′)and R^(2′) be a hydrogen atom. That is, it is preferable that the grouprepresented by general formula (p1) is a group represented by generalformula (p1-1) shown below.

wherein R^(1′), n and Y are the same as R^(1′), n and Y in generalformula (p1) above.

Further, in general formula (p1) above, Y and R^(1′) may be bonded toeach other to form an aliphatic cyclic group.

In such a case, an aliphatic cyclic group is formed by Y, R^(1′),—O—(CH₂)_(n)— and the carbon atom having R^(2′) bonded thereto. Such analiphatic cyclic group is preferably a 4 to 7-membered ring, and morepreferably a 4 to 6-membered ring. Specific examples of the aliphaticcyclic group include a tetrahydropyranyl group and a tetrahydrofuranylgroup.

As the structural unit (a1), it is preferable to use at least one memberselected from the group consisting of structural units represented byformula (a1-0-1) shown below and structural units represented by formula(a1-0-2) shown below.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; and X¹ represents an acid dissociable,dissolution inhibiting group.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; X² represents an acid dissociable,dissolution inhibiting group; and Y² represents a divalent linkinggroup.

In general formula (a1-0-1) shown above, a lower alkyl group and ahalogenated lower alkyl group for R are the same as the lower alkylgroup and halogenated lower alkyl group which can be bonded to theα-position of the aforementioned acrylate ester.

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is as defined for R in general formula(a1-0-1) above.

X² is the same as X¹ in general formula (a1-0-1).

As the divalent linking group for Y², an alkylene group, a divalentaliphatic cyclic group, or a divalent linking group containing a heteroatom is preferable.

When Y² represents an alkylene group, it preferably has 1 to 10 carbonatoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4carbon atoms, and most preferably 1 to 3 carbon atoms.

When Y² represents a divalent aliphatic cyclic group, as the aliphaticcyclic group, the same as those exemplified above in connection with theexplanation of “aliphatic cyclic group” can be used, except that two ormore hydrogen atoms have been removed therefrom. It is particularlydesirable that the aliphatic cyclic group be a group in which two ormore hydrogen atoms have been removed from cyclopentane, cyclohexane,norbornane, isobornane, adamantane, tricyclodecane ortetracyclododecane.

When Y² represents a divalent linking group containing a hetero atom,examples of the divalent linking groups containing a hetero atom include—O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (in the formula,the H may be replaced with a substituent such as an alkyl group or anacyl group), —S—, —S(═O)₂—, —S(═O)₂—O—, a group represented by formula-A-O—B—, and a group represented by formula -[A-C(═O)—O]_(m)—B—. Here,each of A and B independently represents a divalent hydrocarbon groupwhich may have a substituent, and m represents an integer of 0 to 3.

When Y² represents a divalent linking group —NH— and the H in theformula is replaced with a substituent such as an alkyl group or an acylgroup, the substituent preferably has 1 to 10 carbon atoms, morepreferably has 1 to 8 carbon atoms, and most preferably has 1 to 5carbon atoms.

When Y² is a group represented by formula -A-O—B— or a group representedby formula -[A-C(═O)—O]_(m)—B—, each of A and B independently representsa divalent hydrocarbon group which may have a substituent.

m is an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

The hydrocarbon group represented by A may be either an aliphatichydrocarbon group or an aromatic hydrocarbon group. An aliphatichydrocarbon group refers to a hydrocarbon group having no aromaticity.

The aliphatic hydrocarbon group represented by A may be either saturatedor unsaturated, but in general, the aliphatic hydrocarbon group ispreferably saturated.

More specific examples of the aliphatic hydrocarbon group represented byA include linear or branched aliphatic hydrocarbon groups, and aliphatichydrocarbon groups that contain a ring within their structures.

In the “linear or branched aliphatic hydrocarbon group” represented byA, the number of carbon atoms is preferably within a range from 1 to 10,more preferably within a range from 1 to 8, even more preferably withina range from 1 to 5, and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, linear alkylene groups arepreferred, and specific examples include a methylene group, an ethylenegroup [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylenegroup [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂— and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂— and—CH₂CH(CH₃)CH₂CH₂—. The alkyl groups within these alkylalkylene groupsare preferably linear alkyl groups of 1 to 5 carbon atoms.

The linear aliphatic hydrocarbon groups may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated lower alkyl group of 1 to 5 carbon atoms which issubstituted by a fluorine atom, and an oxygen atom (═O).

Examples of the “aliphatic hydrocarbon groups that contain a ring withintheir structures” represented by A include cyclic aliphatic hydrocarbongroups (groups in which two hydrogen atoms have been removed from analiphatic hydrocarbon ring), and groups in which this type of cyclicaliphatic hydrocarbon group is either bonded to the terminal of theabovementioned linear aliphatic hydrocarbon group or positioned partwayalong the linear aliphatic hydrocarbon group.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably has 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic group, a group in which twohydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbonatoms is preferable. Examples of the monocycloalkane includecyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane of 7 to 12 carbon atoms is preferable.Specific examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon groups may or may not have asubstituent. Examples of substituents include a lower alkyl group of 1to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group of 1to 5 carbon atoms which is substituted by a fluorine atom, and an oxygenatom (═O).

The group A is preferably a linear aliphatic hydrocarbon group, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, particularly preferably a methylgroup or an ethyl group, and most preferably an ethyl group.

Examples of the hydrocarbon group represented by B include the samedivalent hydrocarbon groups as those exemplified above in relation tothe hydrocarbon group represented by A.

As the group B, a linear or branched aliphatic hydrocarbon group ispreferred, and a methylene group, an ethylene group or an alkylmethylenegroup is particularly desirable. The alkyl group within thealkylmethylene group is preferably a linear alkyl group of 1 to 5 carbonatoms, is more preferably a linear alkyl group of 1 to 3 carbon atoms,and is most preferably a methyl group.

Further, in the group represented by formula -[A-C(═O)—O]_(m)—B—, m isan integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0or 1, and most preferably 1.

In the present invention, as the divalent linking group for Y², adivalent linking group containing a hetero atom is preferable, and alinear group having an oxygen atom as a hetero atom, for example, agroup that includes an ester bond is particularly desirable.

Of these divalent linking groups, groups represented by theaforementioned formula -A-O—B— or formula -A-C(═O)—O—B— are preferable,and a group represented by formula —(CH₂)_(a)—C(═O)—O—(CH₂)_(b)— isparticularly desirable.

a represents an integer of 1 to 5, is preferably 1 or 2, and is mostpreferably 2.

b represents an integer of 1 to 5, is preferably 1 or 2, and is mostpreferably 1.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

wherein X′ represents a tertiary alkyl ester-type acid dissociable,dissolution inhibiting group; Y represents a lower alkyl group of 1 to 5carbon atoms or an aliphatic cyclic group; n represents an integer of 0to 3; Y² and R represent a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; and R^(1′) and R^(2′) each independentlyrepresent a hydrogen atom or a lower alkyl group of 1 to 5 carbon atoms.

In general formulas (a1-1) to (a1-4), the lower alkyl group andhalogenated lower alkyl group for R are the same as the lower alkylgroup and halogenated lower alkyl group which can be bonded to theα-position of the aforementioned acrylate ester.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ in the formula above are the same as theabove-exemplified tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups for X¹.

As R^(1′), R^(2′), n and Y, may be exemplified by the same R^(1′),R^(2′), n and Y as defined for general formula (p1) described above inconnection with the “acetal-type acid dissociable, dissolutioninhibiting group”.

Examples of Y² include the same divalent linking groups as thoseexemplified above for Y² in the above general formula (a1-0-2).

Specific examples of structural units represented by the above generalformulas (a1-1) to (a1-4) are shown below.

In the following formulas, Rα represents a hydrogen atom, a methyl groupor a trifluoromethyl group.

As the structural unit (a1), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

Of the above, structural units represented by general formula (a1-1) or(a1-3) are preferable. More specifically, at least one structural unitselected from the group consisting of structural units represented byformulas (a1-1-1) to (a-1-1-4), (a1-1-20) to (a1-1-23) and (a1-3-25) to(a1-3-32) is more preferable.

As the structural unit (a1), structural units represented by generalformula (a1-1-01) shown below, which include the structural unitsrepresented by formulas (a1-1-1) to (a1-1-3), structural unitsrepresented by general formula (a1-1-02) shown below, which include thestructural units represented by formulas (a1-1-16) to (a1-1-17) andformulas (a1-1-20) to (a1-1-23), structural units represented by generalformula (a1-3-01) shown below, which include the structural unitsrepresented by formulas (a1-3-25) to (a1-3-26), structural unitsrepresented by general formula (a1-3-02) shown below, which include thestructural units represented by formulas (a1-3-27) to (a1-3-28), andstructural units represented by general formula (a1-3-03) shown beloware also preferable.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; and R¹¹ represents a lower alkyl group.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R¹² represents a lower alkyl group; and hrepresents an integer of 1 to 6.

In general formula (a1-1-01), R is as defined for R in general formula(a1-0-1) above. The lower alkyl group for R¹¹ is the same as the loweralkyl group for R above, and is preferably a methyl group, an ethylgroup or an isopropyl group.

In general formula (a1-1-02), R is as defined for R in general formula(a1-0-1) above. The lower alkyl group for R¹² is the same as the loweralkyl group for R above. R¹² is preferably a methyl group or an ethylgroup, and most preferably an ethyl group.

h is preferably 1 or 2, and most preferably 2.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R¹⁴ represents a lower alkyl group; R¹³represents a hydrogen atom or a methyl group; and a represents aninteger of 1 to 10.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R¹⁴ represents a lower alkyl group; R¹³represents a hydrogen atom or a methyl group; a represents an integer of1 to 10; and n′ represents an integer of 0 to 3.

In the aforementioned general formulas (a1-3-01) and (a1-3-02), R is asdefined for R in general formula (a1-3) above.

R¹³ is preferably a hydrogen atom.

The lower alkyl group for R¹⁴ is the same as the lower alkyl group forR, and is preferably a methyl group or an ethyl group.

a is preferably an integer of 1 to 8, more preferably an integer of 2 to5, and most preferably 2.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; Y^(2′) and Y^(2″) each independentlyrepresents a divalent linking group; X′ represents an acid dissociable,dissolution inhibiting group; and n represents an integer of 0 to 3.

In general formula (a1-3-03), R is as defined for R in general formula(a1-3) above.

Examples of the divalent linking group represented by Y^(2′) and Y^(2″)include the same divalent linking groups as those exemplified above forY² in the aforementioned general formula (a1-3).

Y^(2′) is preferably a divalent hydrocarbon group that may have asubstituent, more preferably a linear aliphatic hydrocarbon group, andstill more preferably a linear alkylene group. Of these, a linearalkylene group of 1 to 5 carbon atoms is more preferable, and amethylene group and an ethylene group are most preferable.

Y^(2″) is preferably a divalent hydrocarbon group that may have asubstituent, more preferably a linear aliphatic hydrocarbon group, andstill more preferably a linear alkylene group. Of these, a linearalkylene group of 1 to 5 carbon atoms is more preferable, and amethylene group and an ethylene group are most preferable.

The acid dissociable, dissolution inhibiting group represented by X′ isas defined for X′ in general formula (a1-3) above.

X′ is preferably a tertiary alkyl ester-type acid dissociable,dissolution inhibiting group, is more preferably an above-mentionedgroup (i) having a tertiary carbon atom within the ring structure of amonovalent aliphatic cyclic group, and is most preferably a grouprepresented by general formula (1-1) above.

n is an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by formula (a1-3-03), structuralunits represented by general formula (a1-3-03-1) shown below whichinclude the structural units represented by formulas (a1-3-29) and(a1-3-31), and structural units represented by general formula(a1-3-03-2) shown below which includes the structural units representedby formulas (a1-3-30) and (a1-3-32), are particularly desirable.

wherein R is as defined for R in general formula (a1-3) above; R¹⁴ is asdefined for R¹⁴ in general formula (a1-3-01) above; a represents aninteger of 1 to 10; b represents an integer of 1 to 10; and n representsan integer of 0 to 3.

a is preferably an integer of 1 to 5, and is most preferably 1 or 2.

b is preferably an integer of 1 to 5, and is most preferably 1 or 2.

n is preferably 1 or 2.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, andstill more preferably 25 to 50 mol %. By making the amount of thestructural unit (a1) at least as large as 10 mol %, a pattern can beeasily formed using a resist composition prepared from the component(A1). On the other hand, by making the amount of the structural unit(a1) no more than 80 mol %, a good balance can be achieved with theother structural units.

Structural Unit (a2):

The structural unit (a2) is a structural unit derived from an acrylateester containing a lactone-containing cyclic group.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A1) is used in the formation of a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andin enhancing the hydrophilicity, thereby increasing the compatibilitywith the developing solution containing water.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include groupsin which one hydrogen atom has been removed from γ-butyrolactone, andgroups in which one hydrogen atom has been removed from mevaloniclactone. Further, specific examples of lactone-containing polycyclicgroups include groups in which one hydrogen atom has been removed from alactone ring-containing bicycloalkane, tricycloalkane ortetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; each R′ represents, independently, ahydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of1 to 5 carbon atoms or —COOR″, wherein each R″ represents,independently, a hydrogen atom or a linear, branched or cyclic alkylgroup of 1 to 15 carbon atoms; R²⁹ represents a divalent linking group;s′ represents 0 or 1; s″ represents 0 or 1; A″ represents an alkylenegroup of 1 to 5 carbon atoms which may contain an oxygen atom or asulfur atom; and m represents an integer of 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as R in thestructural unit (a1).

Examples of the alkyl group of 1 to 5 carbon atoms for R′ include amethyl group, an ethyl group, a propyl group, an n-butyl group and atert-butyl group. Examples of the alkoxy group of 1 to 5 carbon atomsfor R′ include a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group and a tert-butoxy group. Inconsideration of industrial availability, R′ is preferably a hydrogenatom.

When R″ is a linear or branched alkyl group, it preferably has 1 to 10carbon atoms, and more preferably 1 to 5 carbon atoms.

When R″ is a cyclic alkyl group, it preferably has 3 to 15 carbon atoms,more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbonatoms. Examples thereof include groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane, and which may ormay not be substituted with fluorine atoms or fluorinated alkyl groups.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane, and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

Specific examples of alkylene groups of 1 to 5 carbon atoms which maycontain an oxygen atom or a sulfur atom for A″ include a methylenegroup, ethylene group, n-propylene group, isopropylene group, —O—CH₂—,—CH₂—O—CH₂—, —S—CH₂— and —CH₂—S—CH₂—.

Examples of R²⁹ include the same divalent linking groups as thoseexemplified above for Y² in the above general formula (a1-0-2). As R²⁹,an alkylene group is preferable, and a linear or branched alkylene groupis more preferable. When Y² represents an alkylene group, it preferablyhas 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, stillmore preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbonatoms.

Specific examples of the linear alkylene group include a methylenegroup, an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—] anda tetramethylene group [—(CH₂)₄—]. Specific examples of the branchedalkylene group include various alkylalkylene groups, includingalkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂— and—C(CH₃)(CH₂CH₃)—; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂— and —CH₂(CH₂CH₃)CH—; andalkyltrimethylene groups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—.The alkyl groups within these alkylalkylene groups are preferably alkylgroups of 1 to 2 carbon atoms. As R29, a methylene group is mostpreferred.

In each of the formulas, s′ may be either 0 or 1.

Further, in each of the formulas, s″ may be either 0 or 1, but ispreferably 1.

Specific examples of structural units represented by the aforementionedgeneral formulas (a2-1) to (a2-5) when s′ is 0 are shown below.

In the following formulas, Rα represents a hydrogen atom, a methyl groupor a trifluoromethyl group.

Further, specific examples of preferred structural units represented bythe aforementioned general formulas (a2-1) to (a2-5) when s′ is 1include a group in which —CH₂—C(═O)—O— or —C(CH₃)₂—C(═O)—O— ispositioned between the oxygen atom within a carbonyloxy group (—O—)which is bonded to the α-carbon atom and a lactone-containing cyclicgroup bonded to the oxygen atom in the above formulas.

In the component (A1), as the structural unit (a2), one type ofstructural unit may be used, or two or more types of structural unitsmay be used in combination.

As the structural unit (a2), at least one structural unit selected fromthe group consisting of formulas (a2-1) to (a2-5) is preferable, and atleast one structural unit selected from the group consisting of formulas(a2-1) to (a2-3) is more preferable. Of these, it is particularlydesirable to use at least one structural unit selected from the groupconsisting of structural units represented by chemical formulas(a2-1-1), (a2-2-1), (a2-2-7), (a2-3-1) and (a2-3-5), and structuralunits in which —CH₂—C(═O)—O— or —C(CH₃)₂—C(═O)—O— is positioned betweenthe oxygen atom within a carbonyloxy group (—O—) which is bonded to theα-carbon atom of the above structural units and a lactone-containingcyclic group bonded to the oxygen atom.

In the component (A1), the amount of the structural unit (a2) based onthe combined total of all structural units constituting the component(A1) is preferably 5 to 60 mol %, more preferably 10 to 50 mol %, andstill more preferably 20 to 50 mol %. By making the amount of thestructural unit (a2) at least as large as 5 mol %, the effect of usingthe structural unit (a2) can be satisfactorily achieved. On the otherhand, by making the amount of the structural unit (a2) no more than 60mol %, a good balance can be achieved with the other structural units.

Structural Unit (a3):

The structural unit (a3) is a structural unit derived from an acrylateester containing a polar group-containing aliphatic hydrocarbon group.

When the component (A1) includes the structural unit (a3), thehydrophilicity of the component (A) is improved, and hence, thecompatibility of the component (A1) with the developing solution isimproved. As a result, the alkali solubility of the exposed portionsimproves, which contributes to favorable improvements in the resolution.

Examples of the polar group include a hydroxyl group, a cyano group, acarboxyl group, or a hydroxyalkyl group in which some of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms(namely, a fluorinated alkyl alcohol), although a hydroxyl group isparticularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (and preferably alkylene groups) of 1 to 10 carbonatoms, and polycyclic aliphatic hydrocarbon groups (polycyclic groups).These polycyclic groups can be selected appropriately from the multitudeof groups that have been proposed for the resins of resist compositionsdesigned for use with ArF excimer lasers. The polycyclic grouppreferably has 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, a cyano group, a carboxyl group or a hydroxyalkyl groupin which some of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic groups include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the above-mentioned hydrocarbon group is apolycyclic group, structural units represented by general formula (a3-1)shown below, structural units represented by general formula (a3-2), andstructural units represented by general formula (a3-3) are preferable.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; j represents an integer of 1 to 3; krepresents an integer of 1 to 3; t′ represents an integer of 1 to 3; lrepresents an integer of 1 to 5; and s represents an integer of 1 to 3.

In general formulas (a3-1) to (a3-3), the lower alkyl group andhalogenated lower alkyl group for R are the same as the lower alkylgroup and halogenated lower alkyl group which can be bonded to theα-position of the aforementioned acrylate ester.

In general formula (a3-1), j is preferably 1 or 2, and morepreferably 1. When j is 2, it is preferable that the hydroxyl groups bebonded to the 3rd and 5th positions of the adamantyl group. When j is 1,it is preferable that the hydroxyl group be bonded to the 3rd positionof the adamantyl group. j is preferably 1, and it is particularlydesirable that the hydroxyl group be bonded to the 3rd position of theadamantyl group.

In general formula (a3-2), k is preferably 1. The cyano group ispreferably bonded to the 5th or 6th position of the norbonyl group.

In general formula (a3-3), t′ is preferably 1, l is preferably 1 and sis preferably 1. Further, in formula (a3-3), it is preferable that a2-norbonyl group or 3-norbonyl group be bonded to the terminal of thecarboxy group of the acrylic acid. The fluorinated alkyl alcohol(—(CH₂)₁—C(C_(s)F_(2s+1))₂—OH) is preferably bonded to the 5th or 6thposition of the norbonyl group.

As the structural unit (a3), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In the component (A1), the amount of the structural unit (a3) based onthe combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %.

Structural Unit (a4):

The component (A1) may also have a structural unit (a4) which is otherthan the above-mentioned structural units (a1) to (a3), as long as theeffects of the present invention are not impaired.

As the structural unit (a4), any other structural unit which cannot beclassified as one of the above structural units (a1) to (a3) can be usedwithout any particular limitations, and any of the multitude ofconventional structural units used within resist resins for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

Examples of the structural unit (a4) include a structural unit derivedfrom acrylic acid (hereafter referred to as “structural unit (a4′)”) anda structural unit which contains a non-acid-dissociable aliphaticpolycyclic group and is also derived from an acrylate ester (hereafterreferred to as “structural unit (a4″)”).

With respect to the structural unit (a4′), the term “structural unitderived from acrylic acid” refers to a structural unit which is formedby the cleavage of the ethylenic double bond of acrylic acid.

The term “acrylic acid” is a generic term that includes not only acrylicacid having a hydrogen atom bonded to the carbon atom on the α-position,but also acrylic acid having a substituent (an atom other than ahydrogen atom or a group) bonded to the carbon atom on the α-position.As the substituent, a lower alkyl group or a halogenated lower alkylgroup can be mentioned. With respect to the “structural unit derivedfrom acrylic acid”, the “α-position (the carbon atom on the α-position)”refers to the carbon atom having the carbonyl group bonded thereto,unless specified otherwise.

In the acrylic acid, the lower alkyl group and halogenated lower alkylgroup for the substituent at the α-position are the same as the loweralkyl group and halogenated lower alkyl group for R in theaforementioned structural unit (a1). In the present invention, it ispreferable that a hydrogen atom, a lower alkyl group or a halogenatedlower alkyl group bonded to the α-position of the acrylic acid, morepreferably a hydrogen atom, a lower alkyl group or a fluorinated loweralkyl group. In terms of industrial availability, a hydrogen atom or amethyl group is particularly desirable.

Examples of the aliphatic polycyclic group within the structural unit(a4″) include the same groups as those described above in connectionwith the aforementioned structural unit (a1), and any of the multitudeof conventional polycyclic groups used within the resin component ofresist compositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used. In consideration ofindustrial availability and the like, at least one polycyclic groupselected from amongst a tricyclodecanyl group, an adamantyl group, atetracyclododecanyl group, an isobornyl group, and a norbornyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4″) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

wherein R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group.

In general formulas (a4-1) to (a4-5), the lower alkyl group andhalogenated lower alkyl group for R are the same as the lower alkylgroup and the halogenated lower alkyl group for R of the above-mentionedstructural unit (a1).

When the structural unit (a4′) is included in the component (A1), theamount of the structural unit (a4′) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 15 mol %, and more preferably from 1 to 10mol %.

When the structural unit (a4″) is included in the component (A1), theamount of the structural unit (a4″) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

The component (A1) is preferably a copolymer having the structural units(a1), (a2) and (a3). Examples of such a copolymer include a copolymerconsisting of the structural units (a1), (a2) and (a3), and a copolymerconsisting of the structural units (a1), (a2), (a3) and (a4).

In the component (A), as the component (A1), one type may be used alone,or two or more types may be used in combination.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A1)is not particularly limited, but is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 5,000 to 20,000. Bymaking the weight average molecular weight no more than 50,000, thecomponent (A1) exhibits satisfactory solubility in a resist solvent whenused as a resist. On the other hand, by making the weight averagemolecular weight at least as large as 2,000, dry etching resistance andcross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

[Component (A2)]

As the component (A2), a low molecular compound is preferable, which hasa molecular weight of at least 500 and less than 2,000, and contains anacid dissociable, dissolution inhibiting group exemplified above inconnection with the component (A1) and a hydrophilic group. Specificexamples include compounds containing a plurality of phenol skeletons inwhich a part of the hydrogen atoms within hydroxyl groups have beensubstituted with the aforementioned acid dissociable, dissolutioninhibiting groups.

Preferred examples of the component (A2) include low molecular weightphenolic compounds that are known, for example, as sensitizers or heatresistance improvers for use in non-chemically amplified g-line ori-line resists, wherein some of the hydrogen atoms within hydroxyl groupof these compounds have been substituted with the acid dissociable,dissolution inhibiting groups exemplified above, and any of thesecompounds may be used.

Examples of these low molecular weight phenolic compounds includebis(4-hydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane,2-(4-hydroxyphenyl)-2-(4′-hydroxyphenyl)propane,2-(2,3,4-trihydroxyphenyl)-2-(2′,3′,4′-trihydroxyphenyl)propane,tris(4-hydroxyphenyl)methane,bis(4-hydroxy-3,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-3,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-3-methylphenyl)-3,4-dihydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-4-hydroxyphenylmethane, bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-3,4-dihydroxyphenylmethane,1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene,and dimers, trimers and tetramers of formalin condensation products ofphenols such as phenol, m-cresol, p-cresol and xylenol. Needless to say,the low molecular weight phenolic compound is not limited to theseexamples.

Also, there are no particular limitations on the acid dissociable,dissolution inhibiting group, and suitable examples include the groupsdescribed above.

As the component (A2), one type may be used alone, or two or more typesmay be used in combination.

As the component (A), one type may be used alone, or two or more typesmay be used in combination.

As the component (A), it is preferable to use one containing thecomponent (A1).

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Component (B)>

The component (B) includes an acid generator (B1) (hereafter, referredto as “component (B1)”) consisting of a compound represented by generalformula (b1-11) shown below.

wherein R^(7″) to R^(9″) each independently represent an aryl group oran alkyl group, wherein two of R^(7″) to R^(9″) may be bonded to eachother to form a ring with the sulfur atom, and at least one of R^(7″) toR^(9″) represents a substituted aryl group having a group represented bygeneral formula (I) shown below as a substituent; and X⁻ represents ananion.

[Chemical Formula 34]—O—R^(f)   (I)wherein R^(f) represents a fluorinated alkyl group.

In general formula (b1-11), the aryl group for R^(7″) to R^(9″) may bean unsubstituted aryl group having no substituent or a substituted arylgroup in which a part or all of the hydrogen atoms of the aforementionedunsubstituted aryl group has been substituted with substituents.

Examples of the unsubstituted aryl group include an aryl group having 6to 20 carbon atoms. The aryl group preferably has 6 to 10 carbon atomsbecause it can be synthesized at a low cost. As the aryl group, a phenylgroup or a naphthyl group is particularly desirable.

Examples of the substituent for the substituted aryl group include agroup represented by general formula (I) above, an alkyl group, analkoxy group, an ether group, a halogen atom, a halogenated alkyl group,and a hydroxyl group.

In general formula (I), examples of the fluorinated alkyl group forR^(f) include groups in which part or all of the hydrogen atoms withinthe below described unsubstituted alkyl groups have been substitutedwith a fluorine atom.

The unsubstituted alkyl group may be any of linear, branched or cyclic.Alternatively, the unsubstituted alkyl group may be a combination of alinear or branched alkyl group with a cyclic alkyl group.

The unsubstituted linear alkyl group preferably has 1 to 20 carbonatoms, more preferably 1 to 10 carbon atoms, and still more preferably 1to 8 carbon atoms. Specific examples include a methyl group, an ethylgroup, an n-propyl group, an n-butyl group, an n-pentyl group, ann-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group andan n-decanyl group.

The unsubstituted branched alkyl group preferably has 3 to 20 carbonatoms, more preferably 3 to 10 carbon atoms, and still more preferably 3to 8 carbon atoms. As the branched alkyl group, a tertiary alkyl groupis preferable.

As an example of an unsubstituted cyclic alkyl group, a group in whichone hydrogen atom has been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane can be given. Specific examples include monocycloalkylgroups such as a cyclopentyl group and a cyclohexyl group; andpolycycloalkyl groups such as an adamantyl group, a norbornyl group, anisobornyl group, a tricyclodecanyl group and a tetracyclododecanylgroup.

Examples of the combination of a linear or branched alkyl group with acyclic alkyl group include groups in which a cyclic alkyl group as asubstituent is bonded to a linear or branched alkyl group, and groups inwhich a linear or branched alkyl group as a substituent is bonded to acyclic alkyl group.

As the above-mentioned unsubstituted alkyl group, a linear or branchedalkyl group is preferable, and a linear alkyl group is particularlydesirable.

The fluorinated alkyl group for R^(f) may be either a group in whichpart of the hydrogen atoms within the aforementioned unsubstituted alkylgroup has been substituted with a fluorine atom, or a group in which allof the hydrogen atoms within an unsubstituted alkyl group describedbelow has been substituted with a fluorine atom (i.e., a perfluoroalkylgroup).

The fluorinated alkyl group has 2 or more carbon atoms, and the carbonatom that is adjacent to the oxygen atom (—O—) in general formula (I)preferably has no fluorine atoms bonded thereto, whereas the carbon atomat the terminal of R^(f) preferably has a fluorine atom bonded thereto.

As the fluorinated alkyl group, a linear or branched fluorinated alkylgroup is preferable, and a group represented by general formula (I-1)shown below is particularly desirable.

[Chemical Formula 35]—R^(10″)—R^(11″)  (I-1)wherein R^(10″) represents a linear or branched alkylene group, andR^(11″) represents a linear or branched perfluoroalkyl group.

In formula (I-1), the alkylene group for R^(10″) may be linear orbranched, and is preferably linear. Further, the number of carbon atomswithin the alkylene group is preferably within a range from 1 to 10, andmore preferably within a range from 3 to 5. Specific examples of thealkylene group for R^(10″) include groups in which one hydrogen atom hasbeen removed from the alkyl groups exemplified above as unsubstitutedlinear alkyl groups and unsubstituted branched alkyl groups. As R^(10″),a propylene group is particularly desirable.

The perfluoroalkyl group for R^(11″) may be linear or branched, and ispreferably linear. Further, the number of carbon atoms within theperfluoroalkyl group is preferably within a range from 1 to 10, and morepreferably within a range from 1 to 4. As R^(11″), a nonafluoro-n-butylgroup is particularly desirable.

As the group represented by formula (I-1), a group represented byformula —(CH₂)_(e)—(CF₂)_(f)—CF₃ is particularly desirable (wherein erepresents an integer of 1 to 10, and is preferably an integer of 3 to5; f represents an integer of 0 to 9, and is preferably an integer of 0to 3; and e+f is preferably an integer of 2 to 19, and is morepreferably an integer of 4 to 7).

The alkyl group as the substituent for the aforementioned substitutedaryl group is preferably an alkyl group of 1 to 5 carbon atoms, and amethyl group, an ethyl group, a propyl group, an n-butyl group or atert-butyl group is particularly desirable.

The alkoxy group as the substituent for the aforementioned substitutedaryl group is preferably an alkoxy group having 1 to 5 carbon atoms,more preferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

Examples of the ether group as the substituent for the aforementionedsubstituted aryl group include a group represented by formula —R⁰¹—O—R⁰²(wherein R⁰¹ represents an alkylene group and R⁰² represents an alkylgroup).

The alkylene group for R⁰¹ may be linear, branched or cyclic, and ispreferably linear or branched. Further, the number of carbon atomswithin the alkylene group is preferably within a range from 1 to 10, andmore preferably within a range from 1 to 5. Specific examples of thealkylene group include groups in which one hydrogen atom has beenremoved from the alkyl groups exemplified above as unsubstituted alkylgroups.

The alkyl group for R⁰² may be linear, branched or cyclic, and ispreferably linear or branched. Further, the number of carbon atomswithin the alkyl group is preferably within a range from 1 to 10, andmore preferably within a range from 1 to 5. More specifically, as thealkyl group, groups the same as the unsubstituted alkyl groupsexemplified above can be mentioned.

Preferred examples of the halogen atom as the substituent for theaforementioned substituted aryl group include a fluorine atom and achlorine atom, and a fluorine atom is particularly desirable.

Examples of the halogenated alkyl group as the substituent for theaforementioned substituted aryl group include groups in which part of orall of the hydrogen atoms of the aforementioned alkyl groups exemplifiedabove as substituents have been substituted with halogen atoms. As thehalogen atom within the halogenated alkyl group, an atom the same as thehalogen atoms exemplified above as substituents can be mentioned. As thehalogenated alkyl group, a fluorinated alkyl group is particularlydesirable.

The alkyl group for R^(7″) to R^(9″) is not particularly limited andincludes, for example, a linear, branched or cyclic alkyl group having 1to 10 carbon atoms. In terms of achieving excellent resolution, thealkyl group preferably has 1 to 5 carbon atoms. Specific examplesthereof include a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group,a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group,and a decanyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

When two of R^(7″) to R^(9″) are bonded to each other to form a ringwith the sulfur atom, it is preferable that the two of R^(7″) to R^(9″)form a 3 to 10-membered ring including the sulfur atom, and it isparticularly desirable that the two of R^(7″) to R^(9″) form a 5 to7-membered ring including the sulfur atom.

When two of R^(7″) to R^(9″) are bonded to each other to form a ringwith the sulfur atom, the remaining one of R^(7″) to R^(9″) ispreferably an aryl group. The aryl group is preferably a substitutedaryl group having a group represented by general formula (I) above as asubstituent.

In the present invention, at least one of R^(7″) to R^(9″) represents asubstituted aryl group having a group represented by general formula (I)above as a substituent (hereafter, referred to as a substituted arylgroup (I)).

The number of groups represented by general formula (I) above includedin one substituted aryl group (I) is preferably within a range from 1 to3, and is most preferably 1.

Further, in the substituted aryl group (I), the aryl group to which thegroup represented by formula (I) bonds is preferably a phenyl group or anaphthyl group, and a phenyl group is particularly desirable. In thiscase, the group represented by formula (I) preferably bonds to the paraposition of the phenyl group.

The substituted aryl group (I) may also include another substituentother than the group represented by formula (I). Examples of the othersubstituent include an alkyl group, an alkoxy group, an ether group, ahalogen atom, a halogenated alkyl group, and a hydroxyl group. Theseinclude the same substituents as those described above with respect tothe substituents for the substituted aryl group.

The number of other substituents included in one substituted aryl group(I) is preferably within a range from 0 to 2.

One, two or all three of R^(7″) to R^(9″) may be a substituted arylgroup (I). However, it is most preferable that only one of R^(7″) toR^(9″) be a substituted aryl group (I).

In this case, it is preferable that the remaining two of R^(7″) toR^(9″) either represent an aryl group that may have another substituentother than the group represented by formula (I), or be bonded to eachother to form a ring with the sulfur atom.

When the remaining two of R^(7″) to R^(9″) represent an aryl group thatmay have a substituent, the aryl group is preferably an unsubstitutedaryl group, more preferably a phenyl group or a naphthyl group, and mostpreferably a phenyl group.

Specific examples of preferred cation moiety of the component (B1) areshown below.

wherein R^(10″) and R^(11″) are as defined above for R^(10″) and R^(11″)respectively in general formula (I-1), R¹⁰¹ to R¹⁰⁴ each independentlyrepresents an alkyl group or an alkoxy group, and n3 and n4 eachindependently represents an integer of 0 to 5.

In formulas (b1-c-1) to (b1-c-3), as the alkyl group and alkoxy groupfor R¹⁰¹ to R¹⁰⁴, the same alkyl group and alkoxy group as thosedescribed above as the substituents for the substituted aryl group canbe mentioned.

In formula (b1-11), there is no particular limitation on the anion forX⁻, and any anion moiety can be appropriately selected for use which isknown as an anion moiety of an onium salt-based acid generator.

Preferred examples of the anion for X⁻ include an anion represented bygeneral formula (x-1) shown below.

[Chemical Formula 37]R^(4″)—SO₃ ⁻  (x-1)wherein R^(4″) represents an alkyl group, a halogenated alkyl group, anaryl group or an alkenyl group which may have a substituent.

The alkyl group for R^(4″) may be a linear, branched or cyclic alkylgroup.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 20 carbon atoms, morepreferably 4 to 15 carbon atoms, still more preferably 4 to 10 carbonatoms, and most preferably 6 to 10 carbon atoms.

Examples of the halogenated alkyl group for R^(4″) include groups inwhich some or all of the hydrogen atoms of an above-mentioned linear,branched or cyclic alkyl group have been substituted with halogen atoms.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is particularlydesirable.

In the halogenated alkyl group, the percentage of the number of halogenatoms based on the total number of halogen atoms and hydrogen atoms(halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to100%, and most preferably 100%. Higher halogenation ratios arepreferred, as they result in increased acid strength.

The aryl group for R^(4″) is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R^(4″) is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R^(4″), the expression “may have a substituent” meansthat part of or all of the hydrogen atoms within the alkyl group, thehalogenated alkyl group, the aryl group or the alkenyl group may besubstituted with a substituent (an atom other than a hydrogen atom or agroup).

The number of substituents within R^(4″) may be either 1, or 2 orgreater.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, an oxygen atom (═O), and a group represented by formulaZ-Q¹- [wherein Q¹ represents a divalent linking group containing anoxygen atom, and Z represents a hydrocarbon group of 3 to 30 carbonatoms which may have a substituent].

Examples of the halogen atom include the same halogen atoms as thosedescribed above with respect to the halogenated alkyl group for R^(4″).

Examples of the alkyl group include the same alkyl groups as thosedescribed above for R^(4″).

Examples of the hetero atom include an oxygen atom, a nitrogen atom, anda sulfur atom.

In the group represented by formula Z-Q¹-, Q¹ represents a divalentlinking group containing an oxygen atom.

Q¹ may include another atom other than the oxygen atom. Examples of theatom other than the oxygen atom include a carbon atom, a hydrogen atom,a sulfur atom and a nitrogen atom.

Examples of the divalent linking groups containing an oxygen atominclude non-hydrocarbon, oxygen atom-containing linking groups such asan oxygen atom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amidebond (—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate bond(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,oxygen atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementionednon-hydrocarbon, oxygen atom-containing linking groups and an alkylenegroup include —R⁹¹—O—, −R⁹²—O—C(═O)—, —C(═O)—O—R⁹³—O—C(═O)—,—O—R⁹³—O—C(═O)— and —R⁹²—O—C(═O)—R⁹³—O—C(═O)— (wherein each of R⁹¹ toR⁹³ independently represents an alkylene group).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branchedalkylene group, and the alkylene group preferably has 1 to 12 carbonatoms, more preferably 1 to 5 carbon atoms, and most preferably 1 to 3carbon atoms.

Specific examples of the alkylene group include a methylene group[—CH₂—]; alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂; anethylene group [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂— and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylenegroup [—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as—CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group[—CH₂CH₂CH₂CH₂CH₂—].

As Q¹, a divalent linking group containing an ester bond and/or an etherbond is preferable, and groups represented by formula —O—, —R⁹¹—O—,—R⁹²—O—C(═O)—, —C(═O)—O—, —C(═O)—O—R⁹³—, —C(═O)—O—R⁹³—O—C(═O)—,—O—R⁹³—O—C(═O)— and —R⁹²—O—C(═O)—R⁹³—O—C(═O)— are particularlydesirable.

In the group represented by the formula Z-Q¹-, the hydrocarbon group forZ may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

An aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon group preferably has 3 to 30 carbonatoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to20 carbon atoms, still more preferably 6 to 15 carbon atoms, and mostpreferably 6 to 12 carbon atoms. Here, the number of carbon atoms withina substituent(s) is not included in the number of carbon atoms of thearomatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and anarylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbonatoms, and most preferably 1 carbon atom.

The aromatic hydrocarbon group may have a substituent. For example, apart of the carbon atoms constituting the aromatic ring within thearomatic hydrocarbon group may be substituted with a hetero atom, or ahydrogen atom bonded to the aromatic ring within the aromatichydrocarbon group may be substituted with a substituent.

In the former example, a heteroaryl group in which a part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which a part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned hetero atom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O), —COOR″, —OC(═O)R″, ahydroxyalkyl group, a cyano group or the like can be used. Theabove-mentioned R″ represents a hydrogen atom or a linear, branched orcyclic alkyl group of 1 to 15 carbon atoms.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group include a group in which a part of or all ofthe hydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

R″ within the group —COOR″ or —OC(═O)R″ as the substituent for thearomatic hydrocarbon group is as defined above for R″ in theaforementioned structural unit (a2).

Examples of the hydroxyalkyl group as the substituent for the aromatichydrocarbon group include a group in which at least one hydrogen atom ofthe aforementioned alkyl groups exemplified above as substituents hasbeen substituted with a hydroxyl group.

The aromatic hydrocarbon group for Z is preferably an aryl group whichmay have a substituent, an arylalkyl group or a heteroaryl group.

As the aryl group, an unsubstituted aryl group or an aryl group having ahalogen atom as a substituent (namely, a halogenated aryl group) ispreferable, and a phenyl group, a naphthyl group or a fluorinated phenylgroup is particularly desirable.

As the arylalkyl group, one in which an alkyl group is a methyl group ispreferable, and a naphthylmethyl group or a benzyl group is particularlydesirable.

As the heteroaryl group, one containing a nitrogen atom as a hetero atomis preferable, and a group in which one hydrogen atom has been removedfrom pyridine is particularly desirable.

The aliphatic hydrocarbon group for Z may be a saturated aliphatichydrocarbon group or an unsaturated aliphatic hydrocarbon group, or mayalso be a combination thereof. Further, the aliphatic hydrocarbon groupmay be any of linear, branched or cyclic.

In the aliphatic hydrocarbon group for Z, a part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or a part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group containing a hetero atom.

As the “hetero atom” for Z, there is no particular limitation as long asit is an atom other than a carbon atom and a hydrogen atom, and examplesthereof include a halogen atom, an oxygen atom, a sulfur atom and anitrogen atom. Examples of the halogen atom include a fluorine atom, achlorine atom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist solely of theabove-mentioned hetero atom, or may be a group containing a group oratom other than the above-mentioned hetero atom.

Specific examples of the substituent group for substituting a part ofthe carbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—,—C(═O)—NH—, —NH— (the H may be replaced with a substituent such as analkyl group or an acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When thealiphatic hydrocarbon group is cyclic, the aliphatic hydrocarbon groupmay contain these substituent groups in the ring structure.

Examples of the substituent group for substituting a part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, ann-propoxy group, an iso-propoxy group, an n-butoxy group or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is preferable.

Examples of the aforementioned halogenated alkyl group include a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, a cyclic aliphatic hydrocarbon group (aliphaticcyclic group), or a combination thereof is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15 carbon atoms, and mostpreferably 1 to 10 carbon atoms. Specific examples include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group, a decanylgroup, an undecyl group, a dodecyl group, a tridecyl group, anisotridecyl group, a tetradecyl group, a pentadecyl group, a hexadecylgroup, an isohexadecyl group, a heptadecyl group, an octadecyl group, anonadecyl group, an icosyl group, a henicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and mostpreferably 3 to 10 carbon atoms. Specific examples include a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5 carbon atoms, still more preferably 2 to 4 carbonatoms, and most preferably 3 carbon atoms. Examples of linear monovalentunsaturated hydrocarbon groups include a vinyl group, a propenyl group(an allyl group) and a butynyl group. Examples of branched monovalentunsaturated hydrocarbon groups include a 1-methylpropenyl group and a2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group preferably has 3 to 30carbon atoms, more preferably 5 to 30 carbon atoms, still morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and most preferably 6 to 12 carbon atoms.

Examples thereof include groups in which one or more of the hydrogenatoms have been removed from a monocycloalkane; and groups in which oneor more of the hydrogen atoms have been removed from a polycycloalkanesuch as a bicycloalkane, a tricycloalkane, or a tetracycloalkane.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L5) and (S1) to(S4) shown below.

wherein Q″ represents an alkylene group of 1 to 5 carbon atoms, —O—,—S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m representsan integer of 0 or 1.

In the formula above, as the alkylene group for Q″, R⁹⁴ and R⁹⁵, thesame alkylene groups as those described above for R⁹¹ to R⁹³ can beused.

In these aliphatic cyclic groups, a part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as theaforementioned substituent groups for substituting a part or all of thehydrogen atoms can be used.

In the present invention, Z preferably includes a cyclic group which mayhave a substituent. The cyclic group may be an aromatic hydrocarbongroup which may have a substituent or an aliphatic cyclic group whichmay have a substituent, and an aliphatic cyclic group which may have asubstituent is preferable.

The aromatic hydrocarbon group is preferably a naphthyl group which mayhave a substituent or a phenyl group which may have a substituent.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned groups in which one ormore hydrogen atoms have been removed from polycycloalkanes, theaforementioned groups represented by formulas (L2) to (L5) and (S3) to(S4), and the like are preferable.

In the present invention, R^(4″) preferably has a group represented byformula Z-Q¹- as a substituent. In this case, R^(4″) is preferably agroup represented by formula Z-Q¹-Y¹— (wherein Q¹ and Z are the same asdefined above for Q¹ and Z in the aforementioned formula Z-Q¹-; and Y¹represents an alkylene group of 1 to 4 carbon atoms which may have asubstituent, or a fluorinated alkylene group of 1 to 4 carbon atomswhich may have a substituent).

That is, X⁻ is preferably an anion represented by general formula (x-1)shown below.

[Chemical Formula 39]Z-Q¹-Y¹—SO₃ ⁻  (x-11)wherein Q¹ represents a divalent linking group containing an oxygenatom; Z represents a hydrocarbon group of 3 to 30 carbon atoms which mayhave a substituent; and Y¹ represents an alkylene group of 1 to 4 carbonatoms which may have a substituent, or a fluorinated alkylene group of 1to 4 carbon atoms which may have a substituent.

In formula (x-11), Z and Q¹ are the same as defined above for Z and Q¹in the aforementioned formula Z-Q¹-.

As the alkylene group for Y¹, the same alkylene groups as thosedescribed above for Q¹ having 1 to 4 carbon atoms can be used.

As the fluorinated alkylene group, groups in which part of or all of thehydrogen atoms in the alkylene groups described above are substitutedwith fluorine atoms can be used.

Specific examples of Y¹ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—, —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

As Y¹, a fluorinated alkylene group is preferable, and a fluorinatedalkylene group in which the carbon atom bonded to the adjacent sulfuratom is fluorinated is particularly desirable. Examples of suchfluorinated alkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—,—CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—; —CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Among these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, and —CH₂CF₂CF₂— arepreferable, —CF₂—, —CF₂CF₂— and —CF₂CF₂CF₂— are more preferable, and—CF₂— is particularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group have been substituted withatoms or groups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

Preferred examples of the anions represented by formula (x-11) includeanions represented by general formula (x-11-1) shown below.

wherein Z is the same as defined above for Z in the aforementionedformula Z-Q¹-; Q² represents a single bond or an alkylene group; prepresents an integer of 1 to 3; and m1 to m4 each independentlyrepresents 0 or 1, with the proviso that m2+m3 is 1 or 2.

In the aforementioned formula (x-11-1), p represents an integer of 1 to3, and is preferably 1 or 2.

As the alkylene group for Q², the same alkylene groups for R⁹¹ to R⁹³ asthose described above in relation to Q¹ can be used.

Each of m1 to m4 represents 0 or 1, with the proviso that m2+m3 is 1 or2.

More specifically, examples of the anions represented by general formula(x-11-1) include anions represented by general formula (x-11-10), anionsrepresented by general formula (x-11-20), anions represented by generalformula (x-11-30), and anions represented by general formula (x-11-40)which are shown below.

The anions represented by general formula (x-11-10) are shown below.

In formula (x-11-10), Z, Q², m3 and p are as defined above for Z, Q², m3and p, respectively in the aforementioned general formula (x-11-1).

In formula (x-11-10), Z is preferably an aliphatic cyclic group whichmay have a substituent, a linear aliphatic hydrocarbon group which mayhave a substituent, or an aromatic hydrocarbon group which may have asubstituent. Of these, an aliphatic cyclic group which includes a heteroatom-containing substituent group in the ring structure thereof isparticularly desirable.

As Q², a single bond or a methylene group is particularly desirable.Especially, when Z is an aliphatic cyclic group which may have asubstituent, Q² is preferably a single bond. On the other hand, when Zis an aromatic hydrocarbon group which may have a substituent, Q² ispreferably a methylene group.

Specific examples of preferred anions represented by general formula(x-11-10) are shown below.

wherein Q″ is as defined above for Q″ in the aforementioned formulas(L1) to (L5) and (S1) to (S4); m3 and p are as defined above for m3 andp in the aforementioned general formula (x-11-1); each of R⁷ and R^(7′)independently represents a substituent; each of w1 to w6 independentlyrepresents an integer of 0 to 3; and each of v1 to v2 independentlyrepresents an integer of 0 to 5.

In the above formulas, as the substituent for R⁷, the same groups asthose which the aforementioned aliphatic hydrocarbon group for Z mayhave as a substituent can be used.

In the above formulas, as the substituent for R^(7′), the same groups asthose which the aforementioned aromatic hydrocarbon group for Z may haveas a substituent can be used.

When the subscripts (w1 to w6) of R⁷ and R^(7′) represent an integer of2 or more, the plurality of R⁷ and R^(7′) in the compound (anion) may bethe same or may be different from each other.

Each of w1 to w6 independently and preferably represents an integer of 0to 2, and is most preferably 0.

Each of v1 to v2 independently and preferably represents an integer of 0to 3, and is most preferably 0.

The anions represented by general formula (x-11-20) are shown below.

In formula (x-11-20), Z is the same as defined above for Z in theaforementioned formula Z-Q¹-; p is as defined above for p in theaforementioned general formula (x-11-1); and Q³ represents an alkylenegroup.

In formula (x-11-20), Z is preferably an aliphatic cyclic group whichmay have a substituent, a linear aliphatic hydrocarbon group which mayhave a substituent, or an aromatic hydrocarbon group which may have asubstituent.

As the alkylene group for Q³, the same alkylene groups for R91 to R93 asthose described above in relation to Q¹ can be used.

Specific examples of preferred anions represented by general formula(x-11-20) are shown below.

wherein p is as defined above for p in the aforementioned generalformula (x-11-1); R⁷ and R^(7′) are as defined above for R⁷ and R^(7′)in the aforementioned general formulas (x-11-11) to (x-11-17); each ofw7 to w9 independently represents an integer of 0 to 3; q1 represents aninteger of 1 to 12; and g represents an integer of 1 to 20.

When the subscripts (w7 to w9) of R⁷ and R^(7′) represent an integer of2 or more, the plurality of R⁷ and R^(7′) in the compound (anion) may bethe same or different from each other.

Each of w7 to w9 independently and preferably represents an integer of 0to 2, more preferably 0 or 1, and still more preferably 0.

q1 is preferably 1 to 8, more preferably 1 to 5, and still morepreferably 1 to 3.

g is preferably 1 to 15, and more preferably 1 to 10.

p is preferably 1 or 2, and is most preferably 1.

The anions represented by general formula (x-11-30) are shown below.

In formula (x-11-30), p is as defined above for p in the aforementionedgeneral formula (x-11-1); q2 represents an integer of 0 to 5; R^(7″)represents an alkyl group, an alkoxy group, a halogen atom (excluding afluorine atom), a halogenated alkyl group, a hydroxyl group, an oxygenatom (═O), —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group; andr1 represents an integer of 0 to 2; and r2 represents an integer of 1 to5, with the proviso that 1≦r1+r2≦5.

In formula (x-11-30), q2 is preferably 1 to 4, more preferably 1 or 2,and most preferably 2.

As an alkyl group, an alkoxy group, a halogen atom (excluding a fluorineatom), a halogenated alkyl group, —COOR″, —OC(═O)R″, and a hydroxyalkylgroup for R^(7″), the same groups as those exemplified above which theaforementioned aromatic hydrocarbon group for Z may have as asubstituent can be used.

r1 is most preferably 0.

r2 is preferably 2 to 5, and is most preferably 5.

The anions represented by general formula (x-11-40) are shown below.

In formula (x-11-40), p is as defined above for p in the aforementionedgeneral formula (x-11-1); R⁷ is as defined above for R⁷ in theaforementioned general formulas (x-11-11) to (x-11-17); q3 represents aninteger of 1 to 12; and r3 represents an integer of 0 to 3.

In formula (x-11-40), R⁷ is preferably an alkyl group, an alkoxy group,a halogen atom, a halogenated alkyl group, a hydroxyl group, an oxygenatom (═O) or a cyano group.

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, ann-propoxy group, an iso-propoxy group, an n-butoxy group or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom, and a fluorine atom is preferable.

Examples of the aforementioned halogenated alkyl group include a groupin which a part or all of the hydrogen atoms within an alkyl group of 1to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group,an n-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

When the subscript (r3) of R⁷ represents an integer of 2 or more, theplurality of R⁷ in the compound (anion) may be the same or differentfrom each other.

p is preferably 1 or 2, and is most preferably 1.

q3 is preferably 1 to 5, more preferably 1 to 3, and most preferably 1.

r3 is preferably an integer of 0 to 2, more preferably 0 or 1, and stillmore preferably 0.

Further, as R^(4″), a group having an oxygen atom (═O) as a substituentis also preferable. In such a case, as R^(4″), a group represented byformula R^(10″)—(CH₂)_(n′)— (wherein R^(10″) represents a cyclic alkylgroup of 3 to 20 carbon atoms having an oxygen atom (═O) as asubstituent; and n′ is 0 or 1) is preferable. The expression “having anoxygen atom (═O) as a substituent” means that two hydrogen atoms bondedto one carbon atom that constitutes a cyclic alkyl group of 3 to 20carbon atoms have been substituted with an oxygen atom (═O).

There are no particular limitations on the cyclic alkyl group forR^(10″), with the proviso that it has 3 to 20 carbon atoms, although itpreferably has 4 to 20 carbon atoms and may be either a polycyclic groupor a monocyclic group. Examples thereof include groups in which onehydrogen atom has been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, a tricycloalkane or atetracycloalkane. As the monocyclic group, groups in which one hydrogenatom has been removed from a monocycloalkane of 3 to 8 carbon atoms arepreferable, and specific examples thereof include a cyclopentyl group, acyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Thepolycyclic group preferably has 7 to 12 carbon atoms, and specificexamples thereof include an adamantyl group, a norbornyl group, anisobornyl group, a tricyclodecanyl group, and a tetracyclododecanylgroup.

As R^(10″), a polycyclic alkyl group of 6 to 20 carbon atoms having anoxygen atom (═O) as a substituent is preferable, and groups in which twohydrogen atoms bonded to one carbon atom that constitutes an adamantylgroup, a norbornyl group or a tetracyclododecanyl group have beensubstituted with an oxygen atom (═O) are more preferable from anindustrial point of view, and a norbornyl group having an oxygen atom(═O) as a substituent is particularly desirable.

The alkyl group for R^(10″) may also have another substituent other thanthe oxygen atom. Examples of the substituent include a lower alkyl groupof 1 to 5 carbon atoms.

In formula R^(10″)—(CH₂)_(n′)—, n′ is 0 or 1, and is preferably 1.

When R^(4″) is a group represented by formula R^(10″)—(CH₂)_(n′)—, X⁻ ispreferably a camphor sulfonate ion (namely, an ion obtained by replacingone hydrogen atom in camphor with —SO₃—), and is particularly preferablyan ion represented by the chemical formula (x-12-1) shown below (namely,an ion in which a sulfonate ion (—SO₃ ⁻) is bonded to the carbon atom ofthe methyl group bonded to position 1 of the norbornane ring).

Further, examples of the anions which can be used as X⁻, in addition tothose described above, include anions represented by general formulas(b-3) and (b-4) shown below.

wherein X″ represents an alkylene group of 2 to 6 carbon atoms in whichat least one hydrogen atom has been substituted with a fluorine atom; Y″and Z″ each independently represents an alkyl group or halogenated alkylgroup which may have a substituent; and —SO₂— bonded to Z″ may besubstituted with —C(═O)—.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

The smaller the number of carbon atoms within the alkylene group of X″within the above ranges for the number of carbon atoms, the better thesolubility in a resist solvent.

In the alkylene group of X″, it is preferable that the number ofhydrogen atoms substituted with fluorine atoms is as large as possible,as the acid strength increases, and the transparency to high energyradiation of 200 nm or less or to electron beams is improved. Thepercentage of the fluorine atoms within the alkylene group or alkylgroup, i.e., the fluorination ratio, is preferably from 70 to 100%, morepreferably from 90 to 100%, and it is particularly desirable that thealkylene group or alkyl group be a perfluoroalkylene group orperfluoroalkyl group in which all hydrogen atoms are substituted withfluorine atoms.

The alkyl group for Y″ and Z″ may be a linear, branched or cyclic alkylgroup, and examples thereof include the same alkyl groups as thosedescribed above for R^(4″).

The halogenated alkyl group for Y″ and Z″ is a group in which some orall of the hydrogen atoms of the alkyl group have been substituted withhalogen atoms, and examples thereof include the same halogenated alkylgroups as those described above for R^(4″).

In the halogenated alkyl group, the ratio of the number of halogen atomsrelative to the combined total of halogen atoms and hydrogen atomswithin the halogenated alkyl group (namely, the halogenation ratio (%))is preferably 10 to 100%, is more preferably 50 to 100%, and is mostpreferably 100%. Higher halogenation ratios are preferred, as theyresult in increased acid strength.

As the halogenated alkyl group, a fluorinated alkyl group isparticularly desirable.

The alkyl group or halogenated alkyl group for Y″ and Z″ may have asubstituent.

In the alkyl group for Y″ and Z″, the expression “may have asubstituent” means that some or all of the hydrogen atoms within thealkyl group may be substituted with a substituent. In the halogenatedalkyl group for Y″ and Z″, the expression “may have a substituent” meansthat some or all of the halogen atoms and hydrogen atoms within thehalogenated alkyl group may be substituted with a substituent. Thenumber of substituents within Y″ and Z″ may be either 1, or 2 orgreater.

The substituent which the alkyl group or halogenated alkyl group for Y″and Z″ may have can be any atom or group other than a carbon atom, ahydrogen atom and a halogen atom, and examples thereof include heteroatoms, alkyl groups, and groups represented by formula Z⁵-Q⁵- [wherein,Q⁵ represents a divalent linking group containing an oxygen atom, and Z⁵represents a hydrocarbon group of 3 to 30 carbon atoms which may have asubstituent.].

Among these substituents, examples of the hetero atoms and alkyl groupsinclude the same hetero atoms and alkyl groups as those exemplifiedabove as the substituents for R^(4″).

In the group represented by formula Z⁵-Q⁵-, Q⁵ represents a divalentlinking group containing an oxygen atom.

As Q⁵, the same divalent linking groups containing an oxygen atom asthose described above for Q¹ in the group represented by formula Z-Q¹-can be used.

As Q⁵, a divalent linking group containing an ester bond and/or an etherbond is preferable, and groups represented by formula —O—, —R⁹¹—O—,—R⁹²—O—C(═O)—, —C(═O)—O—, —C(═O)—O—R⁹³— and —C(═O)—O—R⁹³—O—C(═O)—(wherein R⁹¹ to R⁹³ are the same as defined above as the alkylene groupsfor R⁹¹ to R⁹³ described above in relation to Q¹) are particularlydesirable.

In the group represented by formula Z⁵-Q⁵-, Z⁵ represents a hydrocarbongroup of 3 to 30 carbon atoms which may have a substituent.

As Z⁵, the same as those described above for Z in the group representedby formula Z-Q¹- can be used.

Z⁵ is preferably an aliphatic hydrocarbon group, more preferably alinear or cyclic aliphatic hydrocarbon group, and still more preferablya cyclic aliphatic hydrocarbon group.

In the above-mentioned general formula (b-4), —SO₂— bonded to Z″ may besubstituted with —C(═O)—. That is, the anion moiety represented by theabove general formula (b-4) may be an anion moiety represented bygeneral formula (b-4′) shown below.

wherein Y″ and Z″ are as defined above for Y″ and Z″ in the abovegeneral formula (b-4).

In the present invention, at least one of Y″ and Z″ in general formula(b-4) and in formula (b-4′) is preferably a fluorinated alkyl groupwhich may have a substituent.

Especially in general formula (b-4), it is particularly desirable thateither one of Y″ and Z″ be a perfluoroalkyl group, and the other be analkyl group or fluorinated alkyl group which may have a substituent. Informula (b-4′), it is preferable that either one of Y″ and Z″ be aperfluoroalkyl group, and the other be an alkyl group which may have asubstituent, and it is particularly desirable that Y″ be aperfluoroalkyl group and Z″ be an alkyl group which may have asubstituent.

Examples of the anions represented by formula (b-4) or (b-4′) in suchcases described above include anions represented by formulas (b4-1) to(b4-8) as shown below.

wherein R⁷ represents a substituent; each of s1 to s4 independentlyrepresents an integer of 0 to 3; each of z1 to z6 independentlyrepresents an integer of 0 to 3; p″ represents an integer of 0 to 4; m₁₁to m₁₃ are 0 or 1; h represents an integer of 1 to 4; and t representsan integer of 1 to 20.

In the above formulas, as the substituent for R⁷, the same groups asthose which the aforementioned aliphatic hydrocarbon group for Z in thegroup represented by formula Z-Q¹- may have as a substituent can beused.

When the subscripts (s1 to s4) of R⁷ represent an integer of 2 or more,the plurality of R⁷ in the compound (anion) may be the same or differentfrom each other.

s1 to s4 are preferably 0 or 1, and are most preferably 0.

z1 to z6 are preferably 0 or 1.

p″ is preferably 0 to 2.

m₁₂ is preferably 0.

h is preferably 1 or 2, and is most preferably 1.

t is more preferably 1 to 15, and still more preferably 3 to 12.

In the present invention, the anions represented by formulas (b4-1) to(b4-4) are particularly desirable.

Further, examples of the anions which can be used as X⁻, in addition tothose described above, include a methide anion. Examples of the methideanion include anions represented by general formula (b-c1) shown below.

wherein R^(8″) represents an alkyl group of 1 to 10 carbon atoms inwhich at least one hydrogen atom is substituted with a fluorine atom;and R^(9″) represents a hydrocarbon group which may have a substituent,or —SO₂—R⁸.

In general formula (b-c1), R^(8″) represents an alkyl group of 1 to 10carbon atoms in which at least one hydrogen atom is substituted with afluorine atom. The alkyl group may be a linear, branched or cyclic alkylgroup. As R^(8″) in the present invention, a linear or branched alkylgroup is preferable, and a linear alkyl group is more preferable.

When R^(9″) represents a hydrocarbon group which may have a substituentin general formula (b-c1) (the expression “hydrocarbon group which mayhave a substituent” means that a part or all of the hydrogen atomsconstituting the hydrocarbon group may be substituted with asubstituent), the hydrocarbon group for R^(9″) may be either analiphatic hydrocarbon group or an aromatic hydrocarbon group. Specificexamples thereof include the same hydrocarbon groups as those describedabove for Z in the above formula Z-Q¹-.

As R^(9″), an aryl group having a halogen atom as a substituent (namely,a halogenated aryl group), or —SO₂—R^(8″) is preferable. The aryl groupwithin the halogenated aryl group is an aryl group of 6 to 10 carbonatoms such as a phenyl group and a naphthyl group, and examples of thehalogenated aryl group include groups in which a part or all of thehydrogen atoms of the above-mentioned aryl groups have been substitutedwith halogen atoms. As the halogen atom within the halogenated alkylgroup, a fluorine atom is preferable.

R^(8″) in formula —SO₂—R^(8″) is as defined above for R^(8″) in theaforementioned general formula (b-c1).

Among those described above, as X⁻, anions represented by theaforementioned general formula (x-1) are preferred. Of these, an anionin which R^(4″) in general formula (x-1) represents a fluorinated alkylgroup which may have a substituent (namely, a fluorinated alkylsulfonateion which may have a substituent) is particularly desirable.

Further, as the anion represented by general formula (x-1), anionsrepresented by the aforementioned general formula (x-11) are preferred,and an anion in which Y¹ in general formula (x-11) represents afluorinated alkylene group of 1 to 4 carbon atoms which may have asubstituent is particularly desirable.

Furthermore, as X⁻, anions represented by the aforementioned generalformulas (b-3) and (b-4) and anions represented by the aforementionedformula (x-12-1) are also preferred.

As the component (B1), one type may be used alone, or two or more typesmay be used in combination.

The proportion of the component (B1) within the component (B) ispreferably from 1 to 100% by weight, more preferably from 5 to 70% byweight, and still more preferably from 10 to 50% by weight.

In the resist composition of the present invention, the component (B)may further include an acid generator component other than the component(B1) (hereafter, referred to as “component (B2)”).

As the component (B2), there is no particular limitation, and any of theknown acid generators used in conventional chemically amplified resistcompositions can be used. Examples of these acid generators arenumerous, and include onium salt-based acid generators such as iodoniumsalts and sulfonium salts; oxime sulfonate-based acid generators;diazomethane-based acid generators such as bisalkyl or bisaryl sulfonyldiazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate-based acid generators; iminosulfonate-based acidgenerators; and disulfone-based acid generators.

As an onium salt-based acid generator, a compound represented by generalformula (b-1) or (b-2) shown below can be used.

wherein R^(1″) to R^(3″) and R^(5″) to R^(6″) each independentlyrepresent an aryl group or alkyl group which may have a substituent,wherein two of R^(1″) to R^(3′) in formula (b-1) may be bonded to eachother to form a ring with the sulfur atom, and at least one of R^(1″) toR^(3″) represents the aforementioned aryl group; at least one of R^(5″)to R^(6″) represents the aforementioned aryl group; and R^(4″) is asdefined above for R^(4″) in the aforementioned general formula (x-1).

In general formula (b-1), R^(1″) to R^(3″) each independently representan aryl group or alkyl group which may have a substituent. In generalformula (b-1), two of R^(1″) to R^(3″) in formula (b-1) may be bonded toeach other to form a ring with the sulfur atom.

Further, among R^(1″) to R^(3″), at least one group represents an arylgroup. Among R^(1″) to R^(3″), two or more groups are preferably arylgroups, and it is particularly desirable that all of R^(1″) to R^(3″)are aryl groups.

The aryl group for R^(1″) to R^(3″) is not particularly limited, andexamples thereof include an aryl group having 6 to 20 carbon atoms. Thearyl group is preferably an aryl group having 6 to 10 carbon atomsbecause it can be synthesized at a low cost. Specific examples thereofinclude a phenyl group and a naphthyl group.

The aryl group may have a substituent. The expression “having asubstituent” means that some or all of the hydrogen atoms of the arylgroup are substituted with substituents, and examples of the substituentinclude an alkyl group, an alkoxy group, a halogen atom, a hydroxylgroup, an alkoxyalkyloxy group, and a group —O—R⁵⁰—CO—O—R⁵¹ (wherein R⁵⁰represents an alkylene group, and R⁵¹ represents an acid dissociablegroup).

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and most preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,more preferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

Examples of the alkoxyalkyloxy group, with which hydrogen atoms of thearyl group may be substituted, include a group —O—C(R⁴⁷)(R⁴⁸)—O—R⁴⁹(wherein each of R⁴⁷ and R⁴⁸ independently represents a hydrogen atom ora linear or branched alkyl group; R⁴⁹ represents an alkyl group; and R⁴⁷and R⁴⁸ may be bonded to each other to form one ring structure, with theproviso that at least one of R⁴⁷ and R⁴⁸ is a hydrogen atom).

The alkyl group for R⁴⁷ and R⁴⁸ preferably has 1 to 5 carbon atoms, andis preferably an ethyl group or a methyl group, and most preferably amethyl group.

It is preferable that either one of R⁴⁷ and R⁴⁸ be a hydrogen atom andthe other be a hydrogen atom or a methyl group, and it is particularlydesirable that both of R⁴⁷ and R⁴⁸ be a hydrogen atom.

The alkyl group for R⁴⁹ preferably has 1 to 15 carbon atoms, and may belinear, branched or cyclic.

The linear or branched alkyl group for R⁴⁹ preferably has 1 to 5 carbonatoms. Examples thereof include a methyl group, an ethyl group, a propylgroup, an n-butyl group and a tert-butyl group.

The cyclic alkyl group for R⁴⁹ preferably has 4 to 15 carbon atoms, morepreferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbonatoms. Specific examples thereof include groups in which one or morehydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, and which may or may not be substituted with alkylgroups of 1 to 5 carbon atoms, fluorine atoms or fluorinated alkylgroups. Examples of the monocycloalkane include cyclopentane andcyclohexane. Examples of the polycycloalkane include adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane. Of these,a group in which one or more hydrogen atoms have been removed fromadamantane is particularly desirable.

R⁴⁷ and R⁴⁸ may be bonded to each other to form one ring structure. Insuch a case, a cyclic group is formed by R⁴⁷, R⁴⁸, the oxygen atomhaving R⁴⁹ bonded thereto, and the carbon atom having the oxygen atomand R⁴⁸ bonded thereto. Such a cyclic group is preferably a 4 to7-membered ring, and more preferably a 4 to 6-membered ring.

In the group —O—R⁵⁰—CO—O—R⁵¹, with which hydrogen atoms of the arylgroup may be substituted, the alkylene group for R⁵⁰ is preferably alinear or branched alkylene group, and is preferably an alkylene groupof 1 to 5 carbon atoms. Examples of the alkylene group include amethylene group, an ethylene group, a trimethylene group, atetramethylene group and a 1,1-dimethylethylene group.

The acid dissociable group for R⁵¹ is not particularly limited as longas it is an organic group which can be dissociated by the action of acid(the acid generated from the component (B) upon exposure), and examplesthereof include the same as those exemplified above as acid dissociable,dissolution inhibiting groups within the structural unit (a1). Here,unlike the aforementioned acid dissociable, dissolution inhibitinggroup, the acid dissociable group does not necessarily exhibit adissolution inhibiting effect in an alkali developing solution.

Examples of the acid dissociable group include a tertiary alkylester-type acid dissociable group such as a cyclic or chain-liketertiary alkyl group, or an acetal-type acid dissociable group such asan alkoxyalkyl group. Among these, a tertiary alkyl ester-type aciddissociable group is preferable.

Specific examples of the tertiary alkyl ester-type acid dissociablegroup include a 2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group,a 1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropylgroup, a 1-(1-adamantyl)-1-methylbutyl group, a1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethylgroup, a 1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, a 1-(1-cyclohexyl)-1-methylpentylgroup, a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

The alkyl group for R^(1″) to R^(3″) is not particularly limited andincludes, for example, a linear, branched or cyclic alkyl group having 1to 10 carbon atoms. In terms of achieving excellent resolution, thealkyl group preferably has 1 to 5 carbon atoms. Specific examplesthereof include a methyl group, an ethyl group, an n-propyl group, anisopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group,a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group,and a decanyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

The alkyl group may have a substituent. The expression “have asubstituent” means that some or all of the hydrogen atoms of the alkylgroup are substituted with substituents. As the substituent, the samegroups as those which the aforementioned aryl group may have as asubstituent can be used.

When two of R^(1″) to R^(3″) in formula (b-1) are bonded to each otherto form a ring with the sulfur atom, it is preferable that the two ofR^(1″) to R^(3″) form a 3 to 10-membered ring including the sulfur atom,and it is particularly desirable that the two of R^(1″) to R^(3″) form a5 to 7-membered ring including the sulfur atom.

When two of R^(1″) to R^(3″) in formula (b-1) are bonded to each otherto form a ring with the sulfur atom, the remaining one of R^(1″) toR^(3″) is preferably an aryl group. As examples of the aryl group, thesame as the above-mentioned aryl groups for R^(1″) to R^(3″) can beexemplified.

Preferred examples of the cation moiety of the compound represented byformula (b-1) include the cation moieties represented by formulas(I-1-1) to (I-1-10) shown below. Of these, the cation moieties having atriphenylmethane structure such as those represented by formulas (I-1-1)to (I-1-8) are particularly desirable.

In the formulas (I-1-9) to (I-1-10) shown below, each of R⁹ and R¹⁰independently represents a phenyl group or naphthyl group which may havea substituent, an alkyl group of 1 to 5 carbon atoms, an alkoxy group ora hydroxyl group.

u represents an integer of 1 to 3, and is most preferably 1 or 2.

In formula (b-2), R^(5″) and R^(6″) each independently represent an arylgroup or an alkyl group. At least one of R^(5″) and R^(6″) represents anaryl group. It is preferable that both of R^(5″) and R^(6″) represent anaryl group.

As the aryl group for R^(5″) and R^(6″), the same as the aryl groups forR^(1″) to R^(3″) can be exemplified.

As the alkyl group for R^(5″) and R^(6″), the same as the alkyl groupsfor R^(1″) to R^(3″) can be exemplified.

It is particularly desirable that both of R^(5″) and R^(6″) represents aphenyl group.

As R^(4″) in formula (b-2), the same as those mentioned above for R^(4″)in formula (b-1) can be exemplified.

Specific examples of suitable onium salt-based acid generatorsrepresented by formula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

It is also possible to use onium salts in which the anion moiety ofthese onium salts are replaced by methanesulfonate, n-propanesulfonate,n-butanesulfonate, or n-octanesulfonate.

Further, onium salt-based acid generators in which the anion moiety inthe aforementioned general formula (b-1) or (b-2) is replaced by ananion moiety represented by the aforementioned general formula (b-3) or(b-4) (the cation moiety is the same as (b-1) or (b-2)) may also beused.

Furthermore, as the onium salt-based acid generator, a sulfonium salthaving a cation moiety represented by general formula (b-5) or (b-6)shown below may also be used.

wherein R⁴¹ to R⁴⁶ each independently represent an alkyl group, anacetyl group, an alkoxy group, a carboxyl group, a hydroxyl group or ahydroxyalkyl group; n₁ to n₅ each independently represent an integer of0 to 3; and n₆ represents an integer of 0 to 2.

With respect to R⁴¹ to R⁴⁶, the alkyl group is preferably an alkyl groupof 1 to 5 carbon atoms, more preferably a linear or branched alkylgroup, and most preferably a methyl group, an ethyl group, a propylgroup, an isopropyl group, an n-butyl group or a tert-butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or an ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

When the subscripts n₁ to n₆ of R⁴¹ to R⁴⁶ represent an integer of 2 ormore, the plurality of R⁴¹ to R⁴⁶ may be the same or different from eachother.

n₁ is preferably 0 to 2, more preferably 0 or 1, and still morepreferably 0.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

The anion moiety of the sulfonium salt having a cation moietyrepresented by general formula (b-5) or (b-6) is not particularlylimited, and the same anion moieties as those used within previouslyproposed onium salt-based acid generators may be used. Examples of suchanion moieties include fluorinated alkylsulfonate ions such as anionmoieties (R^(4″)SO₃ ⁻) for onium salt-based acid generators representedby general formula (b-1) or (b-2) shown above; and anion moietiesrepresented by general formula (b-3) or (b-4) shown above. Among these,a fluorinated alkylsufonate ion is preferable, a fluorinatedalkylsufonate ion of 1 to 4 carbon atoms is more preferable, and alinear perfluoroalkylsulfonate ion of 1 to 4 carbon atoms isparticularly desirable. Specific examples thereof include atrifluoromethylsulfonate ion, a heptafluoro-n-propylsulfonate ion and anonafluoro-n-butylsulfonate ion.

In the present description, an oximesulfonate-based acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate-based acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

wherein R³¹ and R³² each independently represent an organic group.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The expression “have a substituent”means that some or all of the hydrogen atoms of the alkyl group or thearyl group are substituted with substituents.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably has1 to 10 carbon atoms, still more preferably has 1 to 8 carbon atoms,still more preferably has 1 to 6 carbon atoms, and most preferably has 1to 4 carbon atoms. As the alkyl group, a partially or completelyhalogenated alkyl group (hereinafter, sometimes referred to as a“halogenated alkyl group”) is particularly desirable. The “partiallyhalogenated alkyl group” refers to an alkyl group in which some of thehydrogen atoms are substituted with halogen atoms, and the “completelyhalogenated alkyl group” refers to an alkyl group in which all of thehydrogen atoms are substituted with halogen atoms. Examples of thehalogen atom include a fluorine atom, a chlorine atom, a bromine atomand an iodine atom, and a fluorine atom is particularly desirable. Inother words, the halogenated alkyl group is preferably a fluorinatedalkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, a partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms, and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituent,or a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,an aryl group, or a cyano group is preferable. Examples of the alkylgroup and the aryl group for R³² are the same as those of the alkylgroup and the aryl group for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate-based acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

wherein R³³ represents a cyano group, an alkyl group having nosubstituent, or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent, or ahalogenated alkyl group.

wherein R³⁶ represents a cyano group, an alkyl group having nosubstituent, or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent, or a halogenated alkyl group; and p″ represents 2or 3.

In the aforementioned general formula (B-2), the alkyl group having nosubstituent or the halogenated alkyl group for R³³ preferably has 1 to10 carbon atoms, more preferably has 1 to 8 carbon atoms, and mostpreferably has 1 to 6 carbon atoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably has 70% or more, andmost preferably has 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably has 1 to 4 carbon atoms.The halogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably has 1 to 8carbon atoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably has 70% or more of thehydrogen atoms fluorinated, and still more preferably has 90% or more ofthe hydrogen atoms fluorinated. A completely fluorinated alkyl group inwhich 100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In the aforementioned general formula (B-3), the alkyl group having nosubstituent and the halogenated alkyl group for R³⁶ are the same as thealkyl group having no substituent and the halogenated alkyl group forR³³.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate-based acid generatorsinclude α-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate-based acid generators disclosed in WO 2004/074242A2(Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be exemplified.

Of the aforementioned diazomethane-based acid generators, specificexamples of suitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 11-035551,Japanese Unexamined Patent Application, First Publication No. Hei11-035552 and Japanese Unexamined Patent Application, First PublicationNo. Hei 11-035573 may be preferably used.

Furthermore, poly(bis-sulfonyl)diazomethanes may be exemplified by thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane.

As the component (B2), any one type of these acid generators may be usedalone, or two or more types may be used in combination.

Of these, as the component (B2), an onium salt-based acid generatorhaving an anion in which the aforementioned R^(4″) represents afluorinated alkyl group which may have a substituent (namely, afluorinated alkylsulfonate ion which may have a substituent) ispreferable. An onium salt-based acid generator in which Y¹ in theaforementioned general formula (x-11) represents a fluorinated alkylenegroup of 1 to 4 carbon atoms which may have a substituent isparticularly desirable.

When the component (B2) is included in the component (B), the amount ofthe component (B2) within the component (B) is preferably 10 to 90% byweight, and more preferably 50 to 75% by weight.

The ratio (molar ratio) between the blend quantities of the component(B1) and the component (B2) within the component (B) is preferablywithin a range from (B1):(B2)=9:1 to 1:9, more preferably from 4:1 to1:4, and still more preferably from 1:1 to 1:3.

The total amount of the component (B) within the resist composition ofthe present invention is preferably from 0.5 to 60 parts by weight, morepreferably from 1 to 40 parts by weight, and still more preferably from1 to 30 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (B) is within theabove-mentioned range, formation of a resist pattern can besatisfactorily performed. Further, by virtue of the above-mentionedrange, a uniform solution can be obtained and the storage stabilitybecomes satisfactory.

<Optional Component>

For improving the resist pattern shape and the post exposure stabilityof the latent image formed by the pattern-wise exposure of the resistlayer, the resist composition of the present invention may furthercontain a nitrogen-containing organic compound (D) (hereafter referredto as the component (D)) as an optional component.

A multitude of these components (D) have already been proposed, and anyof these known compounds may be used. Examples thereof include aminessuch as an aliphatic amine and an aromatic amine, and an aliphaticamine, and a secondary aliphatic amine or tertiary aliphatic amine isparticularly preferable. Here, an “aliphatic amine” refers to an aminehaving one or more aliphatic groups, and the aliphatic groups preferablyhave 1 to 20 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of 1 to 20 carbon atoms (i.e., alkylamines oralkyl alcohol amines), and cyclic amines.

Specific examples of the alkylamines and alkyl alcohol amines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decanylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine,tri-n-octanolamine, stearyl diethanolamine and lauryl diethanolamine.Among these, trialkylamines and/or alkyl alcohol amines are preferable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidineand piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine, andtris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine.

Further, as the component (D), an aromatic amine may also be used.Examples of aromatic amines include aniline, pyridine,4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole andderivatives thereof, diphenylamine, triphenylamine, tribenzylamine,2,6-diisopropylaniline, 2,2′-dipyridyl, and 4,4′-dipyridyl.

These compounds can be used either alone, or in combinations of two ormore different compounds.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

Furthermore, in the resist composition of the present invention, forpreventing any deterioration in sensitivity, and improving the resistpattern shape and the post exposure stability of the latent image formedby the pattern-wise exposure of the resist layer, at least one compound(E) (hereafter referred to as the component (E)) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids or derivatives thereof includephosphoric acid, phosphonic acid and phosphinic acid. Among these,phosphonic acid is particularly desirable.

Examples of phosphorus oxo acid derivatives include esters in which ahydrogen atom within the above-mentioned oxo acids is substituted with ahydrocarbon group. Examples of the hydrocarbon group include an alkylgroup of 1 to 5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

As the component (E), an organic carboxylic acid is preferable, andsalicylic acid is particularly desirable.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

<Organic Solvent>

The resist composition of the present invention can be prepared bydissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and any one or morekinds of organic solvents can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone,methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethyl sulfoxide (DMSO).

These organic solvents may be used individually, or as a mixed solventcontaining two or more different solvents.

Among these, propylene glycol monomethyl ether acetate (PGMEA),propylene glycol monomethyl ether (PGME) and ethyl lactate (EL) arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA or PGME with a polar solvent is preferable. The mixing ratio(weight ratio) of the mixed solvent can be appropriately determined,taking into consideration the compatibility of the PGMEA or PGME withthe polar solvent, but is preferably in a range from 1:9 to 9:1, andmore preferably from 2:8 to 8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferablyfrom 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

Further, a mixed solvent of PGME with dimethyl sulfoxide is alsopreferable. In this case, the mixing ratio (former:latter) of such amixed solvent is preferably from 9:1 to 1:9, more preferably from 8:2 to2:8, and most preferably from 7:3 to 5:5.

The amount of the component (S) is not particularly limited, and isadjusted appropriately to a concentration that enables application of acoating solution to a substrate in accordance with the thickness of thecoating film. In general, the component (S) is used in an amount thatyields a solid content for the resist composition that is within a rangefrom 2 to 20% by weight, and preferably from 3 to 15% by weight.

Dissolving of the materials for a resist composition in the component(S) can be conducted by simply mixing and stirring each of the abovecomponents together using conventional methods, and where required, thecomposition may also be mixed and dispersed using a dispersion devicesuch as a dissolver, a homogenizer, or a triple roll mill. Furthermore,following mixing, the composition may also be filtered using a mesh, amembrane filter, or the like.

The resist composition of the present invention is a novel resistcomposition containing the component (B1); i.e., a novel acid generatorwhich was conventionally unknown.

Moreover, in the present invention, the level of defects can also bereduced. The term “defects” refers to general abnormalities within aresist film that are detected when observed from directly above thedeveloped resist film using, for example, a surface defect detectionapparatus (product name: “KLA”) manufactured by KLA-TENCOR Corporation.Examples of these abnormalities include post-developing scum, foam,dust, bridges (structures that bridge different portions of the resistpattern), color irregularities, foreign deposits, and residues.

As the miniaturization of resist patterns progress, in the formation ofa resist pattern using the conventional techniques, problems havearisen, including formation of T-top shapes in line and space patternsand occurrence of “Not Open” defects in contact hole patterns. Inparticular, the occurrence of “Not Open” defects in contact holepatterns has become a serious problem. However, these problems can beameliorated by the use of the resist composition of the presentinvention which contains the component (B1).

The reason that this effect is obtained is not entirely clear, but isthought to be due to the fact that because a fluorinated alkyl grouphaving a low surface free energy is introduced to the cation moiety ofthe component (B1), when a resist film is formed using the resistcomposition of the present invention, uneven distribution of thecomponent (B1) near the resist film surface is observed. That is, it ispresumed that due to uneven distribution of the component (B1) thatincludes a fluorinated alkyl group with high water repellency in theresist film surface, generation of acid and its diffusion efficiencyduring exposure and post exposure baking (PEB) are enhanced, and as aresult, solubility of the component (A) in an alkali developing solutioncan be increased or reduced efficiently (which results in, for example,promotion of the deprotection of the acid dissociable, dissolutioninhibiting group when using a positive resist composition), therebyimproving the shape of the resist pattern and ameliorating “Not Open”defects.

Furthermore, the resist composition of the present invention alsoexhibits favorable levels of lithographic properties such assensitivity, depth of focus (DOF), and in-plane uniformity (CDU) of thedimensions (CD) of the formed resist patterns. Excellent levels of CDUare achieved especially when a resist pattern is formed in a narrowpitch. For example, in the formation of a hole pattern within a narrowpitch, a hole pattern having an excellent shape can be formed withoutcausing the connection of hole edges or exhibiting poor removability(namely, poor resolution).

Further, the resist composition of the present invention has theproperties required of a resist composition used in immersionlithography, namely, favorable lithographic properties and favorableproperties (particularly hydrophobicity) for use within an immersionexposure process, and can therefore be used very favorably for immersionexposure.

That is, by including the component (B1) composed of the compound (b-11)of the present invention, a resist film formed using the resistcomposition of the present invention has a high level of hydrophobicity.In other words, since the component (B1) includes a substituentcontaining a fluorine atom in the cation moiety thereof, a resist filmformed using the resist composition of the present invention has ahigher level of hydrophobicity than a resist film that does not includethe component (B1).

Such a resist film with improved hydrophobicity exhibits an extremelyfavorable water tracking ability, which is required when the immersionexposure is performed using a scanning-type immersion exposureapparatus.

The hydrophobicity of a resist film can be evaluated by measuring thecontact angle thereof against water, for example, the static contactangle (the contact angle between the surface of a water droplet on theresist film in a horizontal state and the resist film surface), thedynamic contact angle (the contact angle at which a water droplet startsto slide when the resist film is inclined (sliding angle), the contactangle at the front-end point of the water droplet in the slidingdirection (advancing angle) and the contact angle at the rear-end pointof the water droplet in the sliding direction (receding angle)). Forexample, the higher the hydrophobicity of a resist film, the higher thestatic angle, advancing angle and receding angle, and smaller thesliding angle.

As shown in FIG. 1, when a flat surface 2 with a liquid droplet 1 placedthereon is gradually inclined, the advancing angle describes the angleθ1 between the surface of the liquid droplet at the bottom edge 1 a ofthe liquid droplet 1 and the flat surface 2 when the liquid droplet 1starts to move (slide) down the flat surface 2. Further, at this point(the point when the liquid droplet 1 starts to move (slide) down theflat surface 2), the angle θ2 between the surface of the liquid dropletat the top edge 1 b of the liquid droplet 1 and the flat surface 2 isthe receding angle, and the inclination angle θ3 of the flat surface 2is the sliding angle.

In the present description, the advancing angle, the receding angle, andthe sliding angle are measured in the following manner.

First, a resist composition solution is spin-coated onto a siliconsubstrate, and is then heated at a temperature of 110° C. for 60 secondsto form a resist film. Subsequently, the contact angles for the resistfilm can be measured using a commercially available measurementapparatus such as a DROP MASTER-700 (product name, manufactured by KyowaInterface Science Co. Ltd.), AUTO SLIDING ANGLE: SA-30DM (product name,manufactured by Kyowa Interface Science Co. Ltd.), or AUTO DISPENSER:AD-31 (product name, manufactured by Kyowa Interface Science Co. Ltd.).

With respect to the resist film obtained using the resist composition ofthe present invention, the static contact angle measured prior toexposure and developing is preferably 70 degrees or more, morepreferably from 70 to 100 degrees, and most preferably from 75 to 100degrees. When the static contact angle is at least as large as 70degrees, the suppression effect on substance elution during theimmersion exposure is enhanced. The reason for this has not beenelucidated yet, but it is presumed that one of the main reasons isrelated to the hydrophobicity of the resist film. More specifically, itis presumed that since an aqueous substance such as water is used as theimmersion medium, higher hydrophobicity has an influence on the swiftremoval of the immersion medium from the surface of the resist filmafter the immersion exposure. On the other hand, when the receding angleis no higher than 100 degrees, the lithography properties becomesatisfactory.

For similar reasons, with respect to the resist film obtained using theresist composition of the present invention, the receding angle measuredprior to exposure and developing is preferably 50 degrees or more, morepreferably from 50 to 150 degrees, still more preferably 50 to 130degrees, and most preferably from 53 to 100 degrees.

Furthermore, with respect to the resist film obtained using the resistcomposition of the present invention, the sliding angle measured priorto exposure and developing is preferably no more than 30 degrees, morepreferably from 5 to 30 degrees, still more preferably from 5 to 25degrees, and most preferably from 5 to 23 degrees. When the slidingangle is no higher than 30 degrees, the suppression effect on substanceelution during the immersion exposure is enhanced. On the other hand,when the sliding angle is at least as large as 5 degrees, thelithography properties become satisfactory.

The magnitude of the various angles described above (the dynamic contactangles (advancing angle, receding angle, and sliding angle) and thestatic contact angle) can be adjusted by adjusting the formulation forthe resist composition (for example, by varying the amount of thecomponent (B1), varying the formulation (namely, the type and proportionof structural units) of the component (A), and adding afluorine-containing additive). For example, by increasing the amount ofthe component (B1), the hydrophobicity of the obtained resistcomposition can be enhanced, and the advancing angle, the receding angleand the static contact angle becomes large, whereas the sliding anglebecomes small.

Further, by using the resist composition of the present invention,elution of a substance from the resist film during immersion exposurecan be suppressed.

That is, as described later in detail, immersion exposure is a method inwhich exposure (immersion exposure) is conducted in a state where theregion between the lens and the resist layer formed on a wafer (which isconventionally filled with air or an inert gas such as nitrogen) isfilled with a solvent (an immersion medium) that has a larger refractiveindex than the refractive index of air. In immersion exposure, when theresist film comes into contact with the immersion medium, elution ofsubstances within the resist film (component (B), component (D), and thelike) into the immersion medium occurs. This elution of a substancecauses phenomenon such as degeneration of the resist film and change inthe refractive index of the immersion medium, thereby adverselyaffecting the lithographic properties. The amount of the elutedsubstance is affected by the properties of the resist film surface(e.g., hydrophilicity, hydrophobicity, and the like). For example, byenhancing the hydrophobicity of the resist film surface, it is presumedthat the degree of substance elution can be reduced.

As a resist film formed using the resist composition of the presentinvention includes the component (B1), the resist film exhibits a higherlevel of hydrophobicity than a resist film that does not include thecomponent (B1). Therefore, according to the resist composition of thepresent invention, elution of a substance during immersion exposure canbe suppressed.

Because it enables suppression of substance elution, using the resistcomposition of the present invention also enables suppression ofdegeneration of the resist film and variation in the refractive index ofthe immersion solvent during immersion exposure. By suppressingfluctuation in the refractive index of the immersion solvent, a resistpattern having an excellent shape can be formed. Further, staining ofthe lens of the exposure apparatus can also be reduced. As a result,protective measures for preventing such staining need not be performed,which contributes to a simplification of both the process and theexposure apparatus.

Furthermore, a resist film formed using the resist composition of thepresent invention is resistant to swelling in water. Therefore, a veryfine resist pattern can be formed with a high level of precision.

Also, the resist composition of the present invention also exhibitsfavorable lithographic properties such as sensitivity, resolution andetching resistance, and when used as a resist in an actual immersionexposure, is capable of forming a favorable resist pattern without anypractical difficulties. For example, by using the resist composition ofthe present invention, a very fine resist pattern with dimensions of,for example, not more than 120 nm can be formed.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the presentinvention includes: forming a resist film on a substrate using theresist composition according to the first aspect of the presentinvention, subjecting the resist film to immersion exposure, andsubjecting the resist film to alkali developing to form a resistpattern.

A preferred example of the method of forming a resist pattern accordingto the present invention is described below, where a resist film isexposed by the immersion exposure. However, the present invention is notlimited to the above example, and the exposure of the resist film can beperformed through a general exposure (dry exposure) which is conductedin air or in an inert gas such as nitrogen.

Firstly, a resist composition of the present invention is applied onto asubstrate using a spinner or the like, and a prebake (post applied bake(PAB)) is conducted to form a resist film.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, the substrate can be exemplified bysubstrates for electronic components, and such substrates having wiringpatterns formed thereon. Specific examples thereof include a siliconwafer, a substrate made of metals such as copper, chromium, iron andaluminum, and a glass substrate. Suitable materials for the wiringpattern include copper, aluminum, nickel, and gold. Further, as thesubstrate, any one of the above-exemplified substrates provided with aninorganic and/or organic film on the surface thereof may also be used.As the inorganic film, an inorganic antireflection film (inorganic BARC)can be used. As the organic film, an organic antireflection film(organic BARC) and an organic film such as a lower-layer organic filmused in a multilayer resist method can be used.

Here, a “multilayer resist method” is a method in which at least onelayer of an organic film (lower-layer organic film) and at least onelayer of a resist film (upper resist film) are provided on a substrate,and a resist pattern formed on the upper resist film is used as a maskto conduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed. Themultilayer resist method can be broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (a double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm is formed (a three-layer resist method).

After formation of a resist film, an organic antireflection film may beprovided on the resist film, thereby forming a triple layer laminateconsisting of the substrate, the resist film and the antireflectionfilm. The antireflection film provided on top of the resist film ispreferably soluble in an alkali developing solution.

The steps up until this point can be conducted by using conventionaltechniques. The operating conditions and the like are preferablyselected appropriately in accordance with the formulation and thecharacteristics of the resist composition being used.

Subsequently, the obtained resist film is subjected to selectiveimmersion exposure (liquid immersion lithography) through a desired maskpattern. At this time, the region between the resist film and the lensat the lowermost point of the exposure apparatus is pre-filled with asolvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

There are no particular limitations on the wavelength used for theexposure, and an ArF excimer laser, a KrF excimer laser, an F₂ laser, orthe like can be used. The resist composition according to the presentinvention is effective for KrF and ArF excimer lasers, and isparticularly effective for an ArF excimer laser.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film formed from the resist composition of the present invention.The refractive index of the immersion medium is not particularly limitedas long as it satisfies the above-mentioned requirements.

Examples of this immersion medium that exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ and C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

A resist composition of the present invention is particularly resistantto any adverse effects caused by water, and because the resultinglithographic properties such as the sensitivity and shape of the resistpattern profile are excellent, water is preferably used as the immersionmedium in the present invention. Furthermore, water is also preferred interms of cost, safety, environmental friendliness, and versatility.

Subsequently, following completion of the immersion exposure step, postexposure baking (PEB) is conducted. A PEB treatment is typicallyconducted under temperature conditions of 80 to 150° C. for 40 to 120seconds, preferably 60 to 90 seconds.

Subsequently, developing is conducted using an alkali developingsolution composed of an aqueous alkali solution such as a 0.1 to 10% byweight aqueous solution of tetramethylammonium hydroxide (TMAH).

Thereafter, a water rinse is preferably conducted with pure water. Thiswater rinse can be conducted, for example, by dripping or spraying wateronto the surface of the substrate while rotating the substrate, andwashes away the developing solution and those portions of the resistcomposition that have been dissolved by the developing solution.

By subsequently drying the resist, a resist pattern is obtained in whichthe resist film (the coating of the resist composition) has beenpatterned into a shape faithful to the mask pattern.

<<Compound>>

A compound according to the third aspect of the present invention is acompound represented by the aforementioned general formula (b1-11)(hereafter, referred to as “compound (b1-11)”).

The compound (b1-11) is the same as the component (B1) in the resistcomposition according to the first aspect of the present invention.

The compound (b1-11) is a novel compound that has been unknown untilnow. Further, the compound (b1-11) is useful as an acid generator of aresist composition.

The compound (b1-11) can be produced by using normal methods.

More specifically, for example, when R^(7″) in the aforementionedgeneral formula (b-11) is an aryl group having one group represented bythe aforementioned formula (I), the compound (hereafter, referred to as“compound (b1-11-1)”) can be produced as follows.

First, a compound represented by general formula (b1-01) shown below isadded to an organic solvent (for example, acetone, dichloromethane,tetrahydrofuran or the like) and cooled, and a compound represented bygeneral formula (b1-02) shown below are added thereto, and reacted. Theresultant is subjected to liquid separation and washing with water, tothereby obtain a compound represented by general formula (b1-03) shownbelow from the organic phase.

The compound represented by general formula (b1-03) shown below and acompound represented by general formula (b1-04) shown below are added toa solution of an organic acid H⁺B⁻ (wherein B⁻ represents an anionmoiety of an organic acid, such as methanesulfonic acid ion), andreacted. Then, pure water and an organic solvent (for example, t-butylmethyl ether (TBME), dichloromethane, tetrahydrofuran or the like) areadded thereto, and the organic phase is collected, to thereby obtain acompound represented by general formula (b1-05) shown below from theorganic phase.

Subsequently, the compound represented by general formula (b1-05) shownbelow is dissolved in a mixed solvent of an organic solvent (forexample, dichloromethane, tetrahydrofuran or the like) and water. Then,an alkali metal salt L⁺X⁻ (wherein L⁺ represents an alkali metal cationsuch as a lithium ion or potassium ion) having a desired anion X⁻ isadded thereto, and reacted. The resultant is subjected to liquidseparation and washing with water, to thereby obtain a compoundrepresented by general formula (b1-11-1) shown below (namely, thecompound (b1-11-1)) from the organic phase.

In formulas in the production example of the compound (b1-11-1), R^(8″)to R^(9″) and X⁻ are the same as R^(8″) to R^(9″) and X⁻ in generalformula (b1-11) above; R^(f) is the same as R^(f) in general formula (I)above; Ar represents an arylene group; B⁻ represents an anion moiety ofan organic acid; L⁺ represents an alkali metal cation; and X_(h)represents a halogen atom.

Examples of the arylene group for Ar include a group which is the arylgroup exemplified above for R^(7″) to R^(9″) in the aforementionedgeneral formula (b1-11) having one hydrogen atom removed therefrom.

As the halogen atom for X_(h), a bromine atom or a chlorine atom ispreferable.

The structure of the obtained compound can be confirmed by a generalorganic analysis method such as ¹H-nuclear magnetic resonance (NMR)spectrometry, ¹³C-NMR spectrometry, ¹⁹F-NMR spectrometry, infraredabsorption (IR) spectrometry, mass spectrometry (MS), elementaryanalysis and X-ray diffraction analysis.

<<Acid Generator>>

An acid generator according to the fourth aspect of the presentinvention is an acid generator including the compound according to thethird aspect of the present invention.

The acid generator is added to a resist composition for use. The resistcomposition to which the acid generator is added can be used for bothdry exposure and immersion exposure, and is especially suited forimmersion exposure.

There are no particular limitations on the resist composition to whichthe acid generator is added, although a chemically amplified resistcomposition including a base component that exhibits changed solubilityin an alkali developing solution under the action of acid, and an acidgenerator component that generates acid upon exposure is ideal.

EXAMPLES

As follows is a more detailed description of the present invention basedon a series of examples, although the scope of the present invention isin no way limited by these examples.

In the NMR analysis, tetramethylsilane (TMS) was used as an internalstandard in ¹H-NMR spectrometry, and hexafluorobenzene was used as aninternal standard in ¹⁹F-NMR spectrometry (the peak of hexafluorobenzenewas regarded as −160 ppm).

Synthesis Example 1

150 g of methyl fluorosulfonyl(difluoro)acetate and 375 g of pure waterwere kept at 10° C. or lower in an ice bath, and 343.6 g of a 30%aqueous solution of sodium hydroxide was dropwise added thereto.Following completion of the dropwise addition, the resultant wasrefluxed at 100° C. for 3 hours, followed by cooling and neutralizingwith concentrated hydrochloric acid. The resulting solution was dropwiseadded to 8,888 g of acetone, and the precipitate was collected byfiltration and dried, thereby obtaining 184.5 g of a compound (1-1),represented by a structural formula shown below, in the form of a whitesolid (purity: 88.9%, yield: 95.5%).

56.2 g of the above-mentioned compound (1-1) and 562.2 g of acetonitrilewere prepared, and 77.4 g of p-toluenesulfonic acid monohydrate wasadded thereto. The resultant was refluxed at 110° C. for 3 hours. Then,the reaction liquid was filtered, and the filtrate was concentrated anddried to obtain a solid. 900 g of t-butyl methyl ether was added to theobtained solid and stirred. Thereafter, the resultant was filtered, andthe residue was dried, thereby obtaining 22.2 g of a compound (1-2),represented by a structural formula shown below, in the form of a whitesolid (purity: 91.0%, yield: 44.9%).

4.34 g of the above-mentioned compound (1-2) (purity: 94.1%), 3.14 g of2-benzyloxyethanol and 43.4 g of toluene were prepared, and 0.47 g ofp-toluenesulfonic acid monohydrate was added thereto. The resultant wasrefluxed at 105° C. for 20 hours. Then, the reaction liquid wasfiltered, and 20 g of hexane was added to the residue and stirred.Thereafter, the resultant was filtered, and the residue was dried,thereby obtaining 1.41 g of a compound (1-3) represented by a structuralformula shown below (yield: 43.1%).

1.00 g of the above-mentioned compound (1-3) and 3.00 g of acetonitrilewere prepared, and 0.82 g of 1-adamantanecarbonyl chloride and 0.397 gof triethylamine were dropwise added thereto while cooling with ice.Following completion of the dropwise addition, the resultant was stirredat room temperature for 20 hours and was then filtered. The obtainedfiltrate was concentrated and solidified, and was then dissolved in 30 gof dichloromethane, followed by washing with water three times.Thereafter, the resulting organic layer was concentrated and dried,thereby obtaining 0.82 g of a compound (1-4) represented by a structuralformula shown below (yield: 41%).

The obtained compound (1-4) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=8.81 (s, 1H, H^(c)), 4.37-4.44 (t,2H, H^(d)), 4.17-4.26 (t, 2H, H^(e)), 3.03-3.15 (q, 6H, H^(b)),1.61-1.98 (m, 15H, Adamantane), 1.10-1.24 (t, 9H, H^(a)).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−106.6.

From the results above, it was confirmed that the compound (1-4) had astructure shown below.

Synthesis Example 2

3.63 g of 2,6-dimethylphenol and 72.65 g of acetone were charged into athree-necked flask, and 12.34 g of potassium carbonate was then addedthereto. The resultant was stirred for 30 minutes, and 23.22 g of4,4,5,5,6,6,7,7,7-nonafluorobutyl iodide was then added thereto, and areaction was effected at 40° C. for 19 hours. The reaction solution wascooled to room temperature and was filtered, and the resulting filtratewas solidified. 11.37 g of t-butyl methyl ether (TBME) was then added tothe obtained solid, and the resultant was washed four times with 11.37 gof pure water. The resultant was then subjected to liquid separation tocollect the organic phase, and the obtained organic phase wasconcentrated, and was then purified by distillation, thereby obtaining8.88 g of a compound (2-1).

The compound (2-1) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=2.03-2.10 (m, 2H, H^(b)), 2.23 (m,6H, H^(d)), 2.43-2.55 (m, 2H, H^(a)), 3.85 (t, 2H, H^(c)), 6.91-7.03 (m,3H, H^(e)).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.5, −121.8, −111.6, −78.3.

From the results shown above, it was confirmed that the compound (2-1)had a structure shown below.

Subsequently, 2.64 g of diphosphorus pentaoxide was added to 38.4 g ofmethanesulfonic acid while stirring, and 8.55 g of the compound (2-1)represented by the above structural formula and 1.88 g ofdiphenylsulfoxide were then added gradually thereto while being cooledwith ice. Thereafter, the resultant was stirred for 24 hours at roomtemperature, and the obtained reaction solution was then gradually addeddropwise to a mixed solvent of 91.3 g of pure water and 152.1 g of TBME.Then, liquid separation was conducted to obtain a water phase. Theobtained water phase was washed twice with 91.3 g of TBME, and was thenextracted twice with 91.3 g of dichloromethane, and the obtaineddichloromethane phase was concentrated to thereby obtain 7.4 g of acompound (2-2) in the form of a viscous solid.

The compound (2-2) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=2.03-2.56 (m, 13H,H^(a)+H^(b)+H^(d)+H^(e)), 3.97 (t, 2H, H^(c)), 7.62 (s, 2H, Ar),7.75-7.87 (m, 10H, Ar).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.5, −121.8, −111.6, −78.3.

From the results shown above, it was confirmed that the compound (2-2)had the structure shown below.

Synthesis Example 3

8.82 g of pure water and 8.82 g of dichloromethane were added to 2.09 gof the compound (2-2) having the above-mentioned structure, and 1.27 gof a compound (1-4) represented by a structural formula shown below wasthen added thereto, and the resultant was stirred at room temperaturefor 3 hours. Thereafter, the resultant was subjected to liquidseparation to collect a dichloromethane phase, and the obtaineddichloromethane phase was washed twice with 8.82 g of dilutedhydrochloric acid, and was then washed four times with 8.82 g of purewater. The resulting dichloromethane phase was concentrated andsolidified, thereby obtaining 2.02 g of a compound (3-1) in the form ofa white solid.

The compound (3-1) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=1.60-1.91 (m, 15H, adamantane),2.03-2.56 (m, 10H, H^(a)+H^(b)+H^(d)), 3.97 (t, 2H, H^(c)), 4.20 (t, 2H,H^(e)), 4.41 (t, 2H, H^(f)), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.1, −121.4, −111.0, −106.7,−77.9.

From the results shown above, it was confirmed that the compound (3-1)had a structure shown below.

Synthesis Example 4

0.384 g of the compound (4-1) represented by a structural formula shownbelow was dissolved in 3.84 g of dichloromethane and 3.84 g of water,and 0.40 g of the compound (1-4) represented by a structural formulashown below was then added to the resulting solution. The resultant wasstirred for 1 hour, and was then subjected to liquid separation tocollect an organic phase. The obtained organic phase was washed threetimes with 3.84 g of water. Thereafter, the resulting organic phase wasconcentrated and solidified, thereby obtaining 0.44 g of a compound(4-2) (yield: 81.5%).

The obtained compound (4-2) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=7.57-7.87(m, 14H, Phenyl), 4.40-4.42(t, 2H, H^(b)), 4.15-4.22 (t, 2H, H^(a)), 2.43 (s, 3H, H^(c)), 1.60-1.93(m, 15H, Adamantane).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−106.7.

From the results shown above, it was confirmed that the compound (4-2)had the structure shown below.

Synthesis Example 5 Synthesis of [Compound 3] (Monomer)

(i)

37.6 g (494 mmol) of glycolic acid, 700 mL of dimethylformamide (DMF),86.5 g (626 mmol) of potassium carbonate, and 28.3 g (170 mmol) ofpotassium iodide were charged into a 2L three-necked flask equipped witha thermometer, a cooling pipe, and a stirrer, followed by being stirringat room temperature for 30 minutes. Then, 300 mL of a dimethylformamidesolution containing 100 g (412 mmol) of 2-methyl-2-adamantylchloroacetate was gradually added thereto. The resultant was heated to40° C., and was then stirred for 4 hours. Following the completion ofthe reaction, 2,000 mL of diethyl ether was added to the reactionmixture, followed by filtration. The resulting solution was washed threetimes with 500 nL of distilled water, followed by crystallization usinga mixed solution containing 300 mL of toluene and 200 mL of heptane,thereby obtaining 78 g of an objective compound (namely,2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol) in the form ofa colorless solid (yield: 67%, GC purity: 99%).

The results of instrumental analysis of the obtained compound were asfollows.

¹H-NMR: 1.59 (d, 2H, J=12.5 Hz), 1.64 (s, 3H), 1.71-1.99 (m, 10H), 2.29(m, 2H), 2.63 (t, 1H, J=5.2 Hz), 4.29 (d, 2H, J=5.2 Hz), 4.67 (s, 2H).

¹³C-NMR: 22.35, 26.56, 27.26, 32.97, 34.54, 36.29, 38.05, 60.54, 61.50,89.87, 165.97, 172.81.

GC-MS: 282 (M⁺, 0.02%), 165 (0.09%), 149 (40%), 148 (100%), 133 (22%),117 (2.57%), 89 (0.40%).

From the results shown above, it was confirmed that the obtainedcompound was 2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol.

(ii)

165 g (584 mmol) of2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol, 2,000 mL oftetrahydrofuran (THF), 105 mL (754 mmol) of triethylamine, and 0.165 g(1,000 ppm) of p-methoxyphenol were added to and dissolved in a 2 Lthree-necked flask equipped with a thermometer, a cooling pipe, and astirrer. Following the completion of the dissolution, 62.7 mL (648 mmol)of methacryloyl chloride was gradually added thereto while cooling in anice bath. The temperature of the resultant was elevated to roomtemperature, and the resultant was stirred for 3 hours. Following thecompletion of the reaction, 1,000 mL of diethyl ether was added thereto,followed by washing with 200 mL of distilled water 5 times. Thereafter,the extraction liquid was concentrated, thereby obtaining 198 g of anobjective compound [compound 3] in the form of a colorless liquid(yield: 97%, GC purity: 99%).

The results of instrumental analysis of the obtained [compound 3] wereas follows.

¹H-NMR: 1.58 (d, J=12.5 Hz, 2H), 1.63 (s, 3H), 1.71-1.89 (m, 8H), 1.98(s, 3H), 2.00 (m, 2H), 2.30 (m, 2H), 4.62 (s, 2H), 4.80 (s, 2H), 5.66(m, 1H), 6.23 (m, 1H).

¹³C-NMR: 18.04, 22.15, 26.42, 27.14, 32.82, 34.38, 36.11, 37.92, 60.44,61.28, 89.42, 126.79, 135.18, 165.61, 166.30, 167.20.

GC-MS: 350 (M⁺, 1.4%), 206 (0.13%), 149 (47%), 148 (100%), 133 (20%), 69(37%).

Synthesis Example 6 Synthesis of Polymer Compound (1)

5.10 g (30 mmol) of a [compound 1] represented by a structural formulashown below, 17.38 g (70 mmol) of a [compound 2] represented by astructural formula shown below, 7.00 g (20 mmol) of a [compound 3]represented by a structural formula shown below, and 5.67 g (24 mmol) ofa [compound 4] represented by a structural formula shown below werecharged into to a 500 mL beaker, and were dissolved in 55.13 g of methylethyl ketone. Then, 4.0 mmol of dimethyl azobisisobutyrate (V-601) as apolymerization initiator was added to and dissolved in the resultingsolution. The reaction solution was dropwise added to 30.62 g of methylethyl ketone heated to 75° C. in a separable flask over 6 hours in anitrogen atmosphere. Following completion of the dropwise addition, thereaction solution was heated for 1 hour while stirring, and was thencooled to room temperature. The resulting polymerization solution wasconcentrated under reduced pressure, and was dropwise added to an excessamount of a mixed solution containing methanol and water so as toprecipitate a reaction product (copolymer). The precipitated reactionproduct was separated by filtration, followed by washing and drying,thereby obtaining 15 g of a polymer compound (1) as an objectivecompound.

With respect to the polymer compound (1), the weight average molecularweight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,000, and the dispersity was 2.0.

Further, the polymer compound (1) was analyzed by carbon 13 nuclearmagnetic resonance spectroscopy (600 MHz, ¹³C-NMR). As a result, it wasfound that the composition of the copolymer (ratio (molar ratio) of therespective structural units within the structural formula shown below)was l/m/n/o=25.3/35.3/14.8/24.6.

Examples 1 to 2, Comparative Example 1

The components shown in Table 1 below were mixed together and dissolvedto obtain positive resist composition solutions.

TABLE 1 Component Component Component (A) (B) (D) Component (S) Example1 (A)-1 (B)-1 (B)-2 (D)-1 (S)-1 [100]  [3.96]  [8.25] [0.23] [2,500]Example 2 (A)-1 (B)-1 — (D)-1 (S)-1 [100] [16.00] [0.23] [2,500]Comparative (A)-1 — (B)-2 (D)-1 (S)-1 Example 1 [100] [11.00] [0.23][2,500] The meanings of the abbreviations used in Table 1 are as shownbelow. The numerical values within the brackets [ ] represent blendquantities (parts by weight). (A)-1: the aforementioned polymer compound(1). (B)-1: the aforementioned compound (3-1). (B)-2: the aforementionedcompound (4-2). (D)-1: diethanolamine. (S)-1: a mixed solvent ofPGMEA/PGME = 6/4 (weight ratio).<Formation of a Resist Pattern by Immersion Exposure>

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied onto a 12-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicanti-reflection film having a film thickness of 85 nm.

Then, each of the resist composition solutions obtained above wasapplied onto the anti-reflection film using a spinner, and was thenprebaked (PAB) on a hotplate at 100° C. for 60 seconds, thereby forminga resist film having a film thickness of 120 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern (6% half tone mask), usingan ArF exposure apparatus NSR-S308F (manufactured by Nikon Corporation,NA (numerical aperture)=0.92).

Thereafter, a post exposure bake (PEB) treatment was conducted at 95° C.for 60 seconds, followed by development for 30 seconds at 23° C. in a2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH). Then, the resist film was washed for 30 seconds with pure water,followed by drying by shaking.

As a result, in each of the examples, a contact hole pattern (hereafter,referred to as “CH pattern”) in which holes with a hole diameter of 110nm were positioned with equal spacing (pitch: 240 nm) was formed on theresist film.

Each of the formed CH patterns was observed from above using a scanningelectron microscope (SEM). As a result, in the CH pattern formed usingthe resist composition of Comparative Example 1, the presence ofnumerous holes having diameters smaller than the target size (i.e., 110nm) was observed. On the other hand, in the CH patterns formed using theresist compositions of Examples 1 and 2, the diameter of each hole was,on the whole, uniform.

<Evaluation of Defects>

Subsequently, a surface defect inspection device KLA2371 (a productname) manufactured by KLA Tencor Corporation was used to observe thesurface of the above-mentioned resist pattern, thereby measuring thenumber of “Not Open” defects thereon. As a result, it was found that thenumber of “Not Open” defects in the resist pattern of ComparativeExample 1 was 508. On the other hand, the number of “Not Open” defectsin the resist pattern of Example 1 was 118, and the number of “Not Open”defects in the resist pattern of Example 2 was 48. Thus, the number of“Not Open” defects in these examples was considerably less than that inComparative Example 1.

From the results shown above, it was confirmed that the compoundaccording to the present invention is useful as an acid generator to beused in a resist composition. Further, the resist composition containingthe compound of the present invention as an acid generator was capableof forming an excellent resist pattern with minimal defects in immersionexposure.

Synthesis Example 7 Synthesis of Compound A

3.63 g of 2,6-dimethylphenol and 72.65 g of acetone were charged into athree-necked flask, and 12.34 g of potassium carbonate was then addedthereto. The resultant was stirred for 30 minutes, and 23.22 g of4,4,5,5,6,6,7,7,7-nonafluoroheptyl iodide was then added thereto, and areaction was effected at 40° C. for 19 hours. The reaction solution wascooled to room temperature and was filtered, and the resulting filtratewas solidified. 11.37 g of TBME was then added to the obtained solid,and the resultant was washed four times with 11.37 g of pure water. Theresultant was then subjected to liquid separation to collect the organicphase, and the obtained organic phase was concentrated, and was thenpurified by distillation, thereby obtaining 8.88 g of a compound A.

The compound A was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=2.03-2.10 (m, 2H, H^(b)), 2.23 (m,6H, H^(d)) 2.43-2.55 (m, 2H, H^(a)), 3.85 (t, 2H, H^(c)), 6.91-7.03 (m,3H, H^(e)).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.5, −121.8, −111.6, −78.3.

From the results shown above, it was confirmed that the compound A had astructure shown below.

Synthesis Example 8 Synthesis of Compound B

2.64 g of diphosphorus pentaoxide was added to 38.4 g of methanesulfonicacid while stirring, and 8.55 g of the compound A represented by theabove structural formula and 1.88 g of diphenylsulfoxide were then addedgradually thereto while cooling with ice. Thereafter, the resultant wasstirred for 24 hours at room temperature, and the obtained reactionsolution was then gradually added dropwise to a mixed solvent of 91.3 gof pure water and 152.1 g of TBME. Then, liquid separation was conductedto obtain a water phase. The obtained water phase was washed twice with91.3 g of TBME, and was then extracted twice with 91.3 g ofdichloromethane, and the obtained dichloromethane phase was concentratedto thereby obtain 7.4 g of a compound B in the form of a viscous solid.

The compound B was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=2.03-2.56 (m, 13H,H^(a)+H^(b)+H^(d)+H^(e)), 3.97 (t, 2H, H^(c)), 7.62 (s, 2H, Ar),7.75-7.87 (m, 10H, Ar).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.5, −121.8, −111.6, −78.3.

From the results shown above, it was confirmed that the compound B hadthe structure shown below.

Synthesis Example 9 Synthesis of Compound C

20.2 g of pure water and 20.2 g of dichloromethane were added to 5.00 gof the compound B having the above-mentioned structure, and 4.30 g of acompound (9-1) was then added thereto, and the resultant was stirred atroom temperature for 3 hours. Thereafter, the resultant was subjected toliquid separation to collect a dichloromethane phase, and the obtaineddichloromethane phase was washed twice with 20.2 g of dilutedhydrochloric acid, and was then washed four times with 20.2 g of purewater. The resulting dichloromethane phase was concentrated andsolidified, thereby obtaining 5.68 g of a compound C in the form of awhite solid.

The compound C was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=1.60-1.91 (m, 15H, adamantane),2.03-2.56 (m, 10H, H^(a)+H^(b)+H^(d)), 3.97 (t, 2H, H^(c)), 4.59 (t, 2H,H^(e)), 7.60 (s, 2H, Ar), 7.75-7.84 (m, 10H, Ar).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.5, −121.8, −111.6, −111.2,−78.3.

From the results shown above, it was confirmed that the compound C hadthe structure shown below.

Synthesis Example 10 Synthesis of Compound D

8.82 g of pure water and 8.82 g of dichloromethane were added to 2.09 gof the compound B represented by a structural formula shown below, and1.27 g of a compound (10-1) represented by a structural formula shownbelow was then added thereto, and the resultant was stirred at roomtemperature for 3 hours. Thereafter, the resultant was subjected toliquid separation to collect a dichloromethane phase, and the obtaineddichloromethane phase was washed twice with 8.82 g of dilutedhydrochloric acid, and was then washed four times with 8.82 g of purewater. The resulting dichloromethane phase was concentrated andsolidified, thereby obtaining 2.02 g of a compound D in the form of awhite solid.

The compound D was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=1.60-1.91 (m, 15H, adamantane),2.03-2.56 (m, 10H, H^(a)+H^(b)+H^(d)), 3.97 (t, 2H, H^(c)), 4.20 (t, 2H,H^(e)), 4.41 (t, 2H, H^(f)), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.1, −121.4, −111.0, −106.7,−77.9.

From the results shown above, it was confirmed that the compound D hadthe structure shown below.

Synthesis Example 11 Synthesis of Compound E

2 g of the compound B represented by a structural formula shown belowwas added to 20 g of dichloromethane and 20 g of water, and theresultant was stirred. Then, 1.83 g of a compound (M⁺X⁻) shown below wasadded thereto, and the resultant was stirred for 1 hour. The reactionsolution was subjected to liquid separation to collect an organicsolvent phase, and the obtained organic solvent phase was washed fourtimes with 20 g of water, and was then concentrated and solidified,thereby obtaining 2.0 g of a compound E.

The compound E was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ (ppm)=0.79-2.89 (m, 31H,H^(a)+H^(b)+H^(d)+Undecanoyl), 3.97 (t, 2H, H^(c)), 4.23 (t, 2H, CH₂),4.41 (t, 2H, CH₂), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar).

¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm)=−123.1, −121.4, −111.0, −106.8,−77.9.

From the results shown above, it was confirmed that the compound E hadthe structure shown below.

Synthesis Examples 12 to 29 Synthesis of Compounds F to W

Products (namely, compounds F to W) composed of anions and cations shownin Tables 2 to 6 were obtained by conducting the same operations asthose described in the above Synthesis Example 11 except that thecompound (M⁺X⁻) was changed to those shown in the following Tables 2 to6 (shown in molar equivalent amounts). Each of the compounds wasanalyzed by NMR. The results are shown in Tables 2 to 6. In Tables 2 to6, the symbol “↑” indicates that the cation in the compounds G to W isthe same as the cation in the compound F.

TABLE 2 Com- Compound Product pound NMR M⁺X⁻ Cation Anion F ¹H-NMR(DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd), 3.97 (t,2H, Hc), 4.40-4.50 (m, 4H, CH2), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H,Ar) ¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −161.5, −160.0, −154.0,−123.1, −121.4, −111.0, −106.7, −77.9

G ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 1.73-2.56 (m, 14H, Ha + Hb + Hd +CH2), 2.49 (m, 1H, CH), 3.34 (m, 1H, CH), 3.88 (t, 1H, CH), 3.97 (t, 2H,Hc), 4.66 (t, 1H, CH), 4.78 (m, 1H, CH), 7.59 (s, 2H, Ar), 7.71-7.89 (m,10H, Ar) ¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1, −121.4, −111.0,−107.7, −77.9

↑

H ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd),3.97 (t, 2H, Hc), 4.54-4.61 (m, 4H, CH2CH2), 7.59 (s, 2H, Ar), 7.71-7.89(m, 12H, Ar+ Py-H), 8.74-8.82 (m, 2H, Py-H) ¹⁹F-NMR (DMSO-d6, 376 MHz):δ (ppm) = −123.1, −121.4, −111.0, −106.5, −77.9

↑

TABLE 3 Compound Product Compound NMR M⁺X⁻ Cation Anion I ¹H-NMR(DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 12H, Ha + Hb + Hd + ONL),2.69-2.73 (m, 1H, ONL), 3.97 (t, 2H, Hc), 4.57 (d, 1H, ONL), 4.71 (d,1H, ONL), 4.97 (s, 1H, ONL), 5.46 (t, 1H, ONL), 7.59 (s, 2H, Ar),7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.2,−121.4, −111.0, −107.1, −77.9

↑

J ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 1.53-1.95 (m, 15H, adamantane),2.03-2.56 (m, 12H, Ha + Hb + Hd + CH2), 3.97 (t, 2H, Hc), 4.20 (t, 2H,CH2), 4.40 (t, 2H, CH2), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar)¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1, −121.4, −111.2, −111.0,−77.9

↑

K ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 1.07-1.33 (m, 5H, Cyclohexyl),1.56-1.59 (m, 1H), Cyclohexyl), 1.73-1.75 (m, 2H, Cyclohexyl), 2.03-2.56(m, 12H, Ha + Hb + Hd + Cyclohexyl), 2.77-2.81 (m, 1H, Cyclohexyl), 3.97(t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6,376 MHz): δ (ppm) = −123.1, −121.4, −111.2, −111.0, −77.9, −74.7

↑

TABLE 4 Product Com- Compound Ca- pound NMR M⁺X⁻ tion Anion L ¹H-NMR(DMSO-d6, 400 MHz): δ (ppm) = 1.55-1.88 (m, 15H, adamantane), 2.03-2.56(m, 10H, Ha + Hb + Hd), 3.97 (t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89(m, 10H, Ar) ¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1, −121.4,−111.2, −111.0, −77.9, −74.5

↑

M ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 1.59 (s, 6H, adaman- tane), 1.99(m, 6H, adamantane), 2.03-2.56 (m, 13H, Ha + Hb + Hd + adamantane), 3.97(t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6,376 MHz): δ (ppm) = −123.1, −121.4, −112.9, −111.0, −77.9, −76.0, −69.2

↑

N ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd),3.97 (t, 2H, Hc), 5.20 (s, 2H, CH2), 7.51-7.96 (m, 19H, Ar+ Naph)¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1, −121.4, −113.7, −111.0,−80.5, −77.9

↑

O ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 1.56 (s, 6H, adaman- tane), 1.96(s, 6H, adamantane), 2.03-2.56 (m, 13H, Ha + Hb + Hd + adamantane), 3.97(t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6,376 MHz): δ (ppm) = −123.1, −121.4, −113.36, −111.0, −77.9, −70.13

↑

TABLE 5 Compound Product Compound NMR M⁺X⁻ Cation Anion P ¹H-NMR(DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd), 3.97 (t,2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6, 376MHz): δ (ppm) = −123.1, −121.4, −111.2, −111.0, −77.9, −73.68

↑

Q ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd),3.97 (t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR(DMSO-d6, 376 MHz): δ (ppm) = −161.1, −149.7, −131.6, −123.1, −121.4,−111.0, −77.9, −76.2

↑

R ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 0.71 (s, 3H, CH3), 1.03 (s, 3H,CH3), 1.22-1.29 (m, 2H, CH2), 1.74-1.89 (m, 2H, CH2), 1.90 (t, 1H, CH),2.03-2.56 (m, 12H, Ha + Hb + Hd + CH), 2.66-2.74 (m, 1H, CH), 2.88 (d,1H, CH), 3.97 (t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar)¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1, −121.4, −111.0, −77.9

↑

S ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd),3.97 (t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR(DMSO-d6, 376 MHz): δ (ppm) = −123.1 −121.4, −111.0, −77.9, −75.0 CF₃SO₃^(⊖) K^(⊕) ↑ CF₃SO₃ ^(⊖)

TABLE 6 Com- Compound Product pound NMR M⁺X⁻ Cation Anion T ¹H-NMR(DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd), 3.97 (t,2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6, 376MHz): δ (ppm) = −123.1, −121.7, −121.4, −112.5, −111.0, −77.9, −77.3C₃F₇SO₃ ^(⊖) K^(⊕) ↑ C₃F₇SO₃ ^(⊖) U ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) =2.03-2.56 (m, 10H, Ha + Hb + Hd), 3.97 (t, 2H, Hc), 7.59 (s, 2H, Ar),7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1,−123.0, −121.4, −116.9, −111.0, −77.9

↑

V ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd),3.97 (t, 2H, Hc), 7.59 (s, 2H, Ar), 7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR(DMSO-d6, 376 MHz): δ (ppm) = −123.1, −121.4, −114.7, −111.0, −77.9,−76.0, −75.9

↑

W ¹H-NMR (DMSO-d6, 400 MHz): δ (ppm) = 2.03-2.56 (m, 10H, Ha + Hb + Hd),3.97 (t, 2H, Hc), 4.45 (s, 2H, anion CH2), 5.21 (dd, 1H, anion CH), 5.41(dd, 1H, anion CH), 5.83-5.92 (m, 1H, anion CH), 7.59 (s, 2H, Ar),7.71-7.89 (m, 10H, Ar) ¹⁹F-NMR (DMSO-d6, 376 MHz): δ (ppm) = −123.1,−121.4, −113.0, −111.0, −80.0, −77.9

↑

Synthesis Example 30 Synthesis of [Compound 5] (Monomer)

(i)

78.1 g (500 mmol) of 5,6-dihydroxy-7-oxanorbornane-2-carboxylic acidγ-lactone, 43.5 g (550 mmol) of pyridine, and 250 g of tetrahydrofuran(THF) were charged into a reaction vessel, and 79.1 g (700 mmol) ofchloroacetyl chloride was then dropwise added thereto at 30° C. or lessusing a dropping funnel. The resulting reaction solution was stirred at25° C. for 18 hours, and ethyl acetate was then added thereto.Subsequently, the resultant was neutralized by adding 10% by weightaqueous solution of potassium carbonate thereto, and the precipitatedcrystals were collected by filtration, followed by washing with water.The obtained crystals were dried, thereby obtaining 85.8 g (369 mmol) of5-chloroacetoxy-6-hydroxy-7-oxanorbornane-2-carboxylic acid γ-lactone(compound (30-1)) (yield: 73.8%).

The obtained compound (30-1) was analyzed by ¹H-NMR. The results areshown below.

¹H-NMR (270 MHz, CDCl₃, ppm, TMS) δ: 5.39 (1H, t, J=5.0 Hz), 4.82 (1H,s), 4.75 (1H, d, J=5.5 Hz), 4.69 (1H, d, J=5.0 Hz), 4.12 (2H, s), 2.77(1H, d, J=1.8, 4.8 5.5 Hz), 2.30 (1H, m), 2.10 (1H, m).

From the results shown above, it was confirmed that the obtainedcompound (30-1) had the structure shown below.

(ii)

Then, 40.7 g (472.9 mmol) of methacrylic acid, 89.1 g (644.9 mmol) ofpotassium carbonate, and 400 g of dimethylformamide (DMF) were chargedinto a 5L four-necked flask equipped with a dropping funnel, athermometer, and a stirrer. Subsequently, a solution formed of 100.0 g(429.9 mmol) of the compound (30-1) having the above-mentioned structureand 650 g DMF was dropwise added thereto at room temperature using thedropping funnel. 28.6 g (172.0 mmol) of potassium iodide was added tothe reaction liquid, and the resultant was then stirred at roomtemperature for 5 hours. Thereafter, ethyl acetate and water were addedto a flask (namely, the reaction vessel), and the resulting reactionmixture was then transferred to a separatory funnel and the obtainedwater phase was discarded. The obtained organic phase was washed withwater, and was then dried and concentrated using magnesium sulfate,thereby obtaining 99.9 g (353.8 mmol) of5-(2′-methacyloyloxyacetoxy-6-hydroxy-7-oxanorbornane-2-carboxylic acidγ-lactone ([compound 5]) (yield: 82.3%).

The obtained [compound 5] was analyzed by ¹H-NMR. The results are shownbelow.

¹H-NMR (270 MHz, CDCl₃, ppm, TMS) δ: 6.23 (1H, s), 5.69 (1H, s), 5.39(1H, t, J=5.0 Hz), 4.82 (1H, s), 4.75 (1H, d, J=5.5 Hz), 4.69 (1H, d,J=5.0 Hz), 4.12 (2H, s), 2.77 (1H, d, J=1.8, 4.8, 5.5 Hz), 2.30 (1H, m),2.10 (1H, m), 1.90 (3H, s).

From the results shown above, it was confirmed that the obtained[compound 5] had a structure shown below.

Synthesis Example 31 Synthesis of Polymer Compound (2)

The [compound 5] having the above-mentioned structure, and the [compound1], [compound 6], [compound 7] and [compound 4] having the followingstructures were added to and dissolved in dimethylformamide (DMF) inamounts based on the proportions of each of the structural units withinan objective polymer compound. Then, dimethyl azobisisobutyrate as apolymerization initiator was added to and dissolved in the resultingsolution. The obtained reaction solution was stirred while being heatedat 80° C. for 6 hours in a nitrogen atmosphere, and was then cooled toroom temperature. Thereafter, the resulting polymerization solution wasdropwise added to an excess amount of mixed solution of methanol/waterto thereby precipitate a polymer. Then, the precipitated polymercompound was separated by filtration, followed by washing and drying,thereby obtaining a polymer compound (2) as an objective compound.

The obtained polymer compound (2) was subjected to GPC measurement. As aresult, it was found that the weight average molecular weight (Mw) was7,000, and the dispersity (Mw/Mn) was 1.7. Further, the polymer compound(2) was analyzed by carbon 13 nuclear magnetic resonance spectroscopy(600 MHz, ¹³C-NMR). As a result, it was found that the polymercomposition thereof (namely, ratio (molar ratio) of the respectivestructural units within the structural formula shown below) wasa1/a2/a3/a4/a5=28/35.5/15/13.5/8.

Example 3, Comparative Example 2

The components shown in Table 7 below were mixed together and dissolvedto obtain positive resist composition solutions.

TABLE 7 Component Component Component Component (A) (B) (D) (S) Example3 (A)-2 (B)-3 (B)-4 (D)-2 (S)-1 [100] [7.5] [2.5] [0.4] [2,700]Comparative (A)-2 (B)-3 — (D)-2 (S)-1 Example 2 [100] [9.8] [0.4][2,700] The meanings of the abbreviations used in Table 7 are as shownbelow. The numerical values within the brackets [ ] represent blendquantities (parts by weight). (A)-2: the aforementioned polymer compound(2). (B)-3: a compound represented by chemical formula (B)-3 shownbelow. (B)-4: a compound represented by chemical formula (B)-4 shownbelow (the aforementioned compound C). (D)-2: tri-n-pentylamine. (S)-1:a mixed solvent of PGMEA/PGME = 6/4 (weight ratio). [Chemical Formula80]

<Evaluation of Lithographic Properties>

By using the obtained resist compositions, resist patterns were formedin the following manner, and lithographic properties thereof wereevaluated.

[Formation of a Resist Pattern]

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied onto an 12-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicanti-reflection film having a film thickness of 89 nm. Then, each of theresist composition solutions obtained above was applied onto theanti-reflection film using a spinner, and was then prebaked (PAB) on ahotplate at 90° C. for 60 seconds and dried, thereby forming a resistfilm having a film thickness of 100 nm.

Subsequently, a coating solution for forming a protection film (productname: TILC-057; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was appliedonto the resist film using a spinner, and then heated at 90° C. for 60seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF exposure apparatus for immersion lithography(product name: NSR-S609B, manufactured by Nikon Corporation, NA(numerical aperture)=1.07, σ Conventional (0.97) w/o POLANO), the resistfilm having a top coat formed thereon was selectively irradiated with anArF excimer laser (193 nm) through a mask pattern.

Next, a post exposure bake (PEB) treatment was conducted at 85° C. for60 seconds, followed by development for 35 seconds at 23° C. in a 2.38%by weight aqueous solution of tetramethylammonium hydroxide (TMAHsolution manufactured by Tokyo Ohka Kogyo Co., Ltd.). Then, the resistfilm was rinsed for 15 seconds with pure water, followed by drying byshaking.

As a result, in each of the examples, a dense, contact hole pattern(hereafter, referred to as “CH pattern”) with a hole diameter of 90 nmand a pitch of 140 nm was formed on the resist film.

Further, the sensitivity during formation of the above CH pattern wasused as the optimum exposure dose (Eop, mJ/cm²) value.

Eop values for each of the positive resist compositions are shown inTable 8.

Furthermore, with the above-mentioned Eop, formation of a sparse(isolated) CH pattern with a hole diameter of 90 nm and a pitch of 540nm was also conducted.

[Evaluation of Depth of Focus (DOF)]

With the above-mentioned Eop, by shifting the focus up and down whereappropriate, the depth of focus (DOF; unit: μm) was determined withinthe range where each of the above-mentioned isolated/dense CH patternswas formed with a successful resolution. The results are shown in Table8.

[Evaluation of In-Plane Uniformity (CDU)]

With respect to each of the formed dense/isolated CH patterns, thecontact-hole diameter (CD) was measured for 25 holes within the samewafer, and from the results, the value of 3 times the standard deviationσ (i.e., 3σ) was calculated as a yardstick of CD uniformity (CDU). Thesmaller this 3σ value is, the higher the level of CDU (i.e., thein-plane uniformity of contact-hole diameter) of the holes formed in theresist film. The results are shown in Table 8.

TABLE 8 DOF (nm) CDU (3σ) Eop Isolated Isolated (mJ/cm²) Dense CH CHDense CH CH Example 3 34.2 360 300 4.55 5.33 Comparative 44.4 360 2406.19 5.40 Example 2

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

INDUSTRIAL APPLICABILITY

The present invention is able to provide a novel compound useful as anacid generator for a resist composition, an acid generator including thecompound, a resist composition containing the acid generator, and amethod of forming a resist pattern that uses the resist composition, andthe invention is therefore extremely useful industrially.

1. A resist composition comprising: a base component (A) which exhibitschanged solubility in an alkali developing solution under action ofacid; and an acid-generator component (B) which generates acid uponexposure, wherein said acid-generator component (B) comprises an acidgenerator (B1) including a compound represented by general formula(b1-11) shown below:

wherein R^(7″) to R^(9″) each independently represent an aryl group oran alkyl group, wherein two of R^(7″) to R^(9″) may be bonded to eachother to form a ring with the sulfur atom, and at least one of R^(7″) toR^(9″) represents a substituted aryl group having a group represented bygeneral formula (I) shown below as a substituent; and X⁻ is an anionrepresented by general formula (b-3), (b-4) or (b-c1) shown below:—O—R^(f)  (1) wherein R^(f) represents a fluorinated alkyl group;

wherein X″ represents an alkylene group of 2 to 6 carbon atoms in whichat least one hydrogen atom has been substituted with a fluorine atom; Y″and Z″ each independently represent an alkyl group or halogenated alkylgroup which may have a substituent; and —SO₂— bonded to Z″ may bereplaced by —C(═O)—; and

wherein R^(8″) represents an alkyl group of 1 to 10 carbon atoms inwhich at least one hydrogen atom is substituted with a fluorine atom;and R^(9″) represents a hydrocarbon group which may have a substituent,or —SO₂—R^(8″).
 2. The resist composition according to claim 1, which isa positive resist composition.
 3. The resist composition according toclaim 2, wherein said base component (A) is a resin component (A1) whichexhibits increased solubility in an alkali developing solution underaction of acid.
 4. The resist composition according to claim 3, whereinsaid resin component (A1) further comprises a structural unit (a1)derived from an acrylate ester having an acid dissociable, dissolutioninhibiting group.
 5. The resist composition according to claim 4,wherein said resin component (A1) further comprises a structural unit(a2) derived from an acrylate ester containing a lactone-containingcyclic group.
 6. The resist composition according to claim 5, whereinsaid resin component (A1) further comprises a structural unit (a3)derived from an acrylate ester containing a polar group-containingaliphatic hydrocarbon group.
 7. The resist composition according toclaim 4, wherein said resin component (A1) further comprises astructural unit (a3) derived from an acrylate ester containing a polargroup-containing aliphatic hydrocarbon group.
 8. The resist compositionaccording to claim 1, which further comprises a nitrogen-containingorganic compound (D).
 9. A compound represented by general formula(b1-11) shown below:

wherein R^(7″) to R^(9″) each independently represent an aryl group oran alkyl group, wherein two of R^(7″) to R^(9″) may be bonded to eachother to form a ring with the sulfur atom, and at least one of R^(7″) toR^(9″) represents a substituted aryl group having a group represented bygeneral formula (I) shown below as a substituent; and X⁻ is an anionrepresented by general formula (b-3), (b-4) or (b-c1) shown below:—O—R^(f)  (1) wherein R^(f) represents a fluorinated alkyl group;

wherein X″ represents an alkylene group of 2 to 6 carbon atoms in whichat least one hydrogen atom has been substituted with a fluorine atom; Y″and Z″ each independently represent an alkyl group or halogenated alkylgroup which may have a substituent; and —SO₂— bonded to Z″ may bereplaced by —C(═O)—; and

wherein R^(8″) represents an alkyl group of 1 to 10 carbon atoms inwhich at least one hydrogen atom is substituted with a fluorine atom;and R^(9″) represents a hydrocarbon group which may have a substituent,or —SO₂—R^(8″).
 10. An acid generator comprising a compound of claim 9.